diff --git a/src/cli.rs b/src/cli.rs
index bc3f15f..b1d2b8f 100644
--- a/src/cli.rs
+++ b/src/cli.rs
@@ -1,6 +1,7 @@
 use std::path::PathBuf;
 
 use clap::{Args, Parser, Subcommand, ValueEnum};
+use uuid::Uuid;
 
 #[derive(Debug, PartialEq, Parser)]
 #[command(name = "onx")]
@@ -57,6 +58,12 @@ pub enum Command {
     #[command(subcommand)]
     command: FilesCommand,
   },
+
+  #[command(about = "Perform operations against the lists in the instance")]
+  Lists {
+    #[command(subcommand)]
+    command: ListsCommand,
+  },
 }
 
 #[derive(Debug, PartialEq, Subcommand)]
@@ -244,6 +251,7 @@ pub enum FilesCommand {
     output: Option<PathBuf>,
   },
 
+  #[command(about = "Upload a file to a field on a record")]
   Upload {
     #[arg(long = "record")]
     #[arg(short = 'r')]
@@ -284,6 +292,7 @@ pub enum FilesCommand {
     modified_date: Option<String>,
   },
 
+  #[command(about = "Delete a file from a field on a record")]
   Delete {
     #[arg(long = "record")]
     #[arg(short = 'r')]
@@ -302,6 +311,33 @@ pub enum FilesCommand {
   },
 }
 
+#[derive(Debug, PartialEq, Subcommand)]
+pub enum ListsCommand {
+  #[command(about = "Add or update an item for a specific list")]
+  SaveItem {
+    #[arg(long = "list")]
+    #[arg(short = 'l')]
+    #[arg(help = "List id for list where the item should be saved")]
+    list_id: i32,
+    
+    #[command(flatten)]
+    body: BodySource,
+  },
+
+  #[command(about = "Delete an item from a specific list")]
+  DeleteItem {
+    #[arg(long = "list")]
+    #[arg(short = 'l')]
+    #[arg(help = "List id for list where the item should be saved")]
+    list_id: i32,
+
+    #[arg(long = "item")]
+    #[arg(short = 'i')]
+    #[arg(help = "Id of the item that should be deleted")]
+    item_id: Uuid,
+  },
+}
+
 #[derive(Debug, PartialEq, Clone, Args, Default)]
 pub struct PagingArgs {
   #[arg(long)]
@@ -994,8 +1030,22 @@ mod tests {
   #[test]
   fn parse_cli_from_when_called_with_files_upload_it_should_return_cli() {
     let result = parse_cli_from([
-      "test", "files", "upload", "-r", "1", "-f", "2", "-i", "doc.pdf", "-n", "renamed.pdf",
-      "-t", "application/pdf", "--notes", "test notes", "--modified-date",
+      "test",
+      "files",
+      "upload",
+      "-r",
+      "1",
+      "-f",
+      "2",
+      "-i",
+      "doc.pdf",
+      "-n",
+      "renamed.pdf",
+      "-t",
+      "application/pdf",
+      "--notes",
+      "test notes",
+      "--modified-date",
       "2026-01-01T00:00:00Z",
     ]);
 
@@ -1052,4 +1102,67 @@ mod tests {
     let err = result.unwrap_err();
     assert_eq!(err.code, 2);
   }
+
+  #[test]
+  fn parse_cli_from_when_called_with_lists_save_item_it_should_return_cli() {
+    let result = parse_cli_from([
+      "test", "lists", "save-item", "-l", "1", "-j", r#"{"name":"Item 1"}"#,
+    ]);
+
+    assert_eq!(
+      result,
+      Ok(Cli {
+        api_key: None,
+        base_url: None,
+        pretty: false,
+        command: Command::Lists {
+          command: ListsCommand::SaveItem {
+            list_id: 1,
+            body: BodySource {
+              json: Some(r#"{"name":"Item 1"}"#.to_string()),
+              file: None,
+              stdin: false,
+            },
+          },
+        },
+      })
+    );
+  }
+
+  #[test]
+  fn parse_cli_from_when_called_with_lists_delete_item_it_should_return_cli() {
+    let result = parse_cli_from([
+      "test",
+      "lists",
+      "delete-item",
+      "-l",
+      "10",
+      "-i",
+      "d3b07384-d113-40e1-a20c-55c3c0a4e70e",
+    ]);
+
+    assert_eq!(
+      result,
+      Ok(Cli {
+        api_key: None,
+        base_url: None,
+        pretty: false,
+        command: Command::Lists {
+          command: ListsCommand::DeleteItem {
+            list_id: 10,
+            item_id: Uuid::parse_str("d3b07384-d113-40e1-a20c-55c3c0a4e70e").unwrap(),
+          },
+        },
+      })
+    );
+  }
+
+  #[test]
+  fn parse_cli_from_when_called_with_lists_without_subcommand_it_should_return_usage_error() {
+    let result = parse_cli_from(["test", "lists"]);
+
+    assert!(result.is_err());
+    let err = result.unwrap_err();
+    assert_eq!(err.code, 2);
+  }
 }
diff --git a/src/client.rs b/src/client.rs
index 02bda5a..feca4ac 100644
--- a/src/client.rs
+++ b/src/client.rs
@@ -1,9 +1,10 @@
 use onspring::{
   App, BatchDeleteRecordsRequest, BatchGetRecordsRequest, CollectionResponse,
   CreatedWithIdResponse, DataFormat, Field, FileInfo, FileResponse, OnspringClient, OnspringError,
-  PagedResponse, PagingRequest, QueryRecordsRequest, Record, SaveFileRequest, SaveRecordRequest,
-  SaveRecordResponse,
+  PagedResponse, PagingRequest, QueryRecordsRequest, Record, SaveFileRequest, SaveListItemRequest,
+  SaveListItemResponse, SaveRecordRequest, SaveRecordResponse,
 };
+use uuid::Uuid;
 
 pub trait OnspringRunner {
   fn ping(&self) -> impl std::future::Future<Output = Result<(), OnspringError>> + Send;
@@ -107,6 +108,18 @@ pub trait OnspringRunner {
     field_id: i32,
     file_id: i32,
   ) -> impl std::future::Future<Output = Result<(), OnspringError>> + Send;
+
+  fn save_list_item(
+    &self,
+    list_id: i32,
+    request: SaveListItemRequest,
+  ) -> impl std::future::Future<Output = Result<SaveListItemResponse, OnspringError>> + Send;
+
+  fn delete_list_item(
+    &self,
+    list_id: i32,
+    item_id: Uuid,
+  ) -> impl std::future::Future<Output = Result<(), OnspringError>> + Send;
 }
 
 impl OnspringRunner for OnspringClient {
@@ -231,6 +244,18 @@ impl OnspringRunner for OnspringClient {
   ) -> Result<(), OnspringError> {
     self.delete_file(record_id, field_id, file_id).await
   }
+
+  async fn save_list_item(
+    &self,
+    list_id: i32,
+    request: SaveListItemRequest,
+  ) -> Result<SaveListItemResponse, OnspringError> {
+    self.save_list_item(list_id, request).await
+  }
+
+  async fn delete_list_item(&self, list_id: i32, item_id: Uuid) -> Result<(), OnspringError> {
+    self.delete_list_item(list_id, item_id).await
+  }
 }
 
 #[cfg(test)]
@@ -299,6 +324,15 @@ pub mod testing {
     pub delete_file_record_id: Mutex<Option<i32>>,
     pub delete_file_field_id: Mutex<Option<i32>>,
     pub delete_file_file_id: Mutex<Option<i32>>,
+
+    pub save_list_item_result: Result<SaveListItemResponse, OnspringError>,
+    pub delete_list_item_result: Result<(), OnspringError>,
+
+    pub save_list_item_list_id: Mutex<Option<i32>>,
+    pub save_list_item_request: Mutex<Option<SaveListItemRequest>>,
+
+    pub delete_list_item_list_id: Mutex<Option<i32>>,
+    pub delete_list_item_item_id: Mutex<Option<Uuid>>,
   }
 
   impl Default for MockClient {
@@ -434,6 +468,17 @@ pub mod testing {
         delete_file_record_id: Mutex::new(None),
         delete_file_field_id: Mutex::new(None),
         delete_file_file_id: Mutex::new(None),
+
+        save_list_item_result: Ok(SaveListItemResponse {
+          id: Uuid::nil(),
+        }),
+        delete_list_item_result: Ok(()),
+
+        save_list_item_list_id: Mutex::new(None),
+        save_list_item_request: Mutex::new(None),
+
+        delete_list_item_list_id: Mutex::new(None),
+        delete_list_item_item_id: Mutex::new(None),
       }
     }
   }
@@ -664,5 +709,27 @@ pub mod testing {
         Err(err) => Err(clone_onspring_error(err)),
       }
     }
+
+    async fn save_list_item(
+      &self,
+      list_id: i32,
+      request: SaveListItemRequest,
+    ) -> Result<SaveListItemResponse, OnspringError> {
+      *self.save_list_item_list_id.lock().unwrap() = Some(list_id);
+      *self.save_list_item_request.lock().unwrap() = Some(request);
+      match &self.save_list_item_result {
+        Ok(res) => Ok(res.clone()),
+        Err(err) => Err(clone_onspring_error(err)),
+      }
+    }
+
+    async fn delete_list_item(&self, list_id: i32, item_id: Uuid) -> Result<(), OnspringError> {
+      *self.delete_list_item_list_id.lock().unwrap() = Some(list_id);
+      *self.delete_list_item_item_id.lock().unwrap() = Some(item_id);
+      match &self.delete_list_item_result {
+        Ok(()) => Ok(()),
+        Err(err) => Err(clone_onspring_error(err)),
+      }
+    }
   }
 }
diff --git a/src/commands/lists.rs b/src/commands/lists.rs
new file mode 100644
index 0000000..c4e0d69
--- /dev/null
+++ b/src/commands/lists.rs
@@ -0,0 +1,372 @@
+use std::io::{Read, Write};
+
+use onspring::SaveListItemRequest;
+use serde::Deserialize;
+use uuid::Uuid;
+
+use crate::cli::ListsCommand;
+use crate::client::OnspringRunner;
+use crate::error::CliResult;
+use crate::output::{SaveListItemResponseOutput, SuccessResponse, write_json};
+use crate::validation::{parse_body, validate_positive_i32};
+
+#[derive(Debug, Clone, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SaveListItemInput {
+  pub id: Option<Uuid>,
+  pub name: String,
+  pub numeric_value: Option<f64>,
+  pub color: Option<String>,
+}
+
+impl From<SaveListItemInput> for SaveListItemRequest {
+  fn from(value: SaveListItemInput) -> Self {
+    Self {
+      id: value.id,
+      name: value.name,
+      numeric_value: value.numeric_value,
+      color: value.color,
+    }
+  }
+}
+
+pub async fn handle<C: OnspringRunner, W: Write>(
+  command: &ListsCommand,
+  client: &C,
+  writer: &mut W,
+  pretty: bool,
+) -> CliResult<()> {
+  handle_with_reader(command, client, writer, std::io::stdin(), pretty).await
+}
+
+pub async fn handle_with_reader<C: OnspringRunner, W: Write, R: Read>(
+  command: &ListsCommand,
+  client: &C,
+  writer: &mut W,
+  reader: R,
+  pretty: bool,
+) -> CliResult<()> {
+  match command {
+    ListsCommand::SaveItem { list_id, body } => {
+      validate_positive_i32(*list_id, "list_id")?;
+      let input: SaveListItemInput = parse_body(body, reader)?;
+      let request: SaveListItemRequest = input.into();
+      let response = client.save_list_item(*list_id, request).await?;
+      let output: SaveListItemResponseOutput = response.into();
+      write_json(writer, &output, pretty)?;
+    }
+    ListsCommand::DeleteItem { list_id, item_id } => {
+      validate_positive_i32(*list_id, "list_id")?;
+      client.delete_list_item(*list_id, *item_id).await?;
+      write_json(writer, &SuccessResponse { ok: true }, pretty)?;
+    }
+  }
+
+  Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+  use super::*;
+  use onspring::{OnspringError, SaveListItemResponse};
+
+  use crate::cli::BodySource;
+  use crate::client::testing::MockClient;
+  use crate::error::CliError;
+
+  // --- SaveItem tests ---
+
+  #[tokio::test]
+  async fn handle_when_save_item_succeeds_it_should_write_save_response() {
+    let item_uuid = Uuid::parse_str("d3b07384-d113-40e1-a20c-55c3c0a4e70e").unwrap();
+    let mock_client = MockClient {
+      save_list_item_result: Ok(SaveListItemResponse { id: item_uuid }),
+      ..Default::default()
+    };
+
+    let command = ListsCommand::SaveItem {
+      list_id: 1,
+      body: BodySource {
+        json: Some(
+          r##"{"id":"d3b07384-d113-40e1-a20c-55c3c0a4e70e","name":"Item 1","numericValue":10.5,"color":"#ffffff"}"##
+            .to_string(),
+        ),
+        file: None,
+        stdin: false,
+      },
+    };
+    let mut buffer = Vec::new();
+
+    let result = handle(&command, &mock_client, &mut buffer, false).await;
+
+    assert_eq!(result, Ok(()));
+
+    let written = String::from_utf8(buffer).unwrap();
+    assert_eq!(
+      written.trim(),
+      r#"{"id":"d3b07384-d113-40e1-a20c-55c3c0a4e70e"}"#
+    );
+    assert_eq!(*mock_client.save_list_item_list_id.lock().unwrap(), Some(1));
+    let req = mock_client
+      .save_list_item_request
+      .lock()
+      .unwrap()
+      .clone()
+      .unwrap();
+    assert_eq!(req.id, Some(item_uuid));
+    assert_eq!(req.name, "Item 1");
+    assert_eq!(req.numeric_value, Some(10.5));
+    assert_eq!(req.color, Some("#ffffff".to_string()));
+  }
+
+  #[tokio::test]
+  async fn handle_when_save_item_succeeds_pretty_it_should_write_pretty_json() {
+    let item_uuid = Uuid::parse_str("d3b07384-d113-40e1-a20c-55c3c0a4e70e").unwrap();
+    let mock_client = MockClient {
+      save_list_item_result: Ok(SaveListItemResponse { id: item_uuid }),
+      ..Default::default()
+    };
+
+    let command = ListsCommand::SaveItem {
+      list_id: 1,
+      body: BodySource {
+        json: Some(r#"{"name":"New Item"}"#.to_string()),
+        file: None,
+        stdin: false,
+      },
+    };
+    let mut buffer = Vec::new();
+
+    let result = handle(&command, &mock_client, &mut buffer, true).await;
+
+    assert_eq!(result, Ok(()));
+
+    let written = String::from_utf8(buffer).unwrap();
+    let expected = concat!(
+      "{\n",
+      "  \"id\": \"d3b07384-d113-40e1-a20c-55c3c0a4e70e\"\n",
+      "}"
+    );
+    assert_eq!(written.trim(), expected);
+  }
+
+  #[tokio::test]
+  async fn handle_when_save_item_with_invalid_list_id_it_should_return_usage_error() {
+    let mock_client = MockClient::default();
+
+    let command = ListsCommand::SaveItem {
+      list_id: 0,
+      body: BodySource {
+        json: Some(r#"{"name":"Item"}"#.to_string()),
+        file: None,
+        stdin: false,
+      },
+    };
+    let mut buffer = Vec::new();
+
+    let result = handle(&command, &mock_client, &mut buffer, false).await;
+
+    assert_eq!(
+      result,
+      Err(CliError::usage("list_id must be greater than 0."))
+    );
+    assert!(buffer.is_empty());
+  }
+
+  #[tokio::test]
+  async fn handle_when_save_item_has_missing_body_it_should_return_usage_error() {
+    let mock_client = MockClient::default();
+
+    let command = ListsCommand::SaveItem {
+      list_id: 1,
+      body: BodySource::default(),
+    };
+    let mut buffer = Vec::new();
+
+    let result = handle(&command, &mock_client, &mut buffer, false).await;
+
+    assert_eq!(
+      result,
+      Err(CliError::usage(
+        "A request body is required. Provide --json, --file, or --stdin."
+      ))
+    );
+    assert!(buffer.is_empty());
+  }
+
+  #[tokio::test]
+  async fn handle_when_save_item_reads_from_stdin() {
+    let item_uuid = Uuid::parse_str("d3b07384-d113-40e1-a20c-55c3c0a4e70e").unwrap();
+    let mock_client = MockClient {
+      save_list_item_result: Ok(SaveListItemResponse { id: item_uuid }),
+      ..Default::default()
+    };
+
+    let command = ListsCommand::SaveItem {
+      list_id: 5,
+      body: BodySource {
+        json: None,
+        file: None,
+        stdin: true,
+      },
+    };
+    let mut buffer = Vec::new();
+    let stdin_data = r#"{"name":"From Stdin","numericValue":2.0}"#;
+
+    let result = handle_with_reader(
+      &command,
+      &mock_client,
+      &mut buffer,
+      stdin_data.as_bytes(),
+      false,
+    )
+    .await;
+
+    assert_eq!(result, Ok(()));
+    let written = String::from_utf8(buffer).unwrap();
+    assert_eq!(
+      written.trim(),
+      r#"{"id":"d3b07384-d113-40e1-a20c-55c3c0a4e70e"}"#
+    );
+    let req = mock_client
+      .save_list_item_request
+      .lock()
+      .unwrap()
+      .clone()
+      .unwrap();
+    assert_eq!(req.name, "From Stdin");
+    assert_eq!(req.numeric_value, Some(2.0));
+  }
+
+  #[tokio::test]
+  async fn handle_when_save_item_fails_it_should_return_mapped_cli_error() {
+    let mock_client = MockClient {
+      save_list_item_result: Err(OnspringError::Api {
+        status_code: 400,
+        message: "Invalid list item".to_string(),
+      }),
+      ..Default::default()
+    };
+
+    let command = ListsCommand::SaveItem {
+      list_id: 1,
+      body: BodySource {
+        json: Some(r#"{"name":"Item"}"#.to_string()),
+        file: None,
+        stdin: false,
+      },
+    };
+    let mut buffer = Vec::new();
+
+    let result = handle(&command, &mock_client, &mut buffer, false).await;
+
+    assert_eq!(
+      result,
+      Err(CliError::runtime(
+        "API request failed (400): Invalid list item"
+      ))
+    );
+    assert!(buffer.is_empty());
+  }
+
+  // --- DeleteItem tests ---
+
+  #[tokio::test]
+  async fn handle_when_delete_item_succeeds_it_should_write_success_response() {
+    let item_uuid = Uuid::parse_str("d3b07384-d113-40e1-a20c-55c3c0a4e70e").unwrap();
+    let mock_client = MockClient {
+      delete_list_item_result: Ok(()),
+      ..Default::default()
+    };
+
+    let command = ListsCommand::DeleteItem {
+      list_id: 1,
+      item_id: item_uuid,
+    };
+    let mut buffer = Vec::new();
+
+    let result = handle(&command, &mock_client, &mut buffer, false).await;
+
+    assert_eq!(result, Ok(()));
+
+    let written = String::from_utf8(buffer).unwrap();
+    assert_eq!(written.trim(), r#"{"ok":true}"#);
+    assert_eq!(*mock_client.delete_list_item_list_id.lock().unwrap(), Some(1));
+    assert_eq!(
+      *mock_client.delete_list_item_item_id.lock().unwrap(),
+      Some(item_uuid)
+    );
+  }
+
+  #[tokio::test]
+  async fn handle_when_delete_item_succeeds_pretty_it_should_write_pretty_json() {
+    let item_uuid = Uuid::parse_str("d3b07384-d113-40e1-a20c-55c3c0a4e70e").unwrap();
+    let mock_client = MockClient {
+      delete_list_item_result: Ok(()),
+      ..Default::default()
+    };
+
+    let command = ListsCommand::DeleteItem {
+      list_id: 1,
+      item_id: item_uuid,
+    };
+    let mut buffer = Vec::new();
+
+    let result = handle(&command, &mock_client, &mut buffer, true).await;
+
+    assert_eq!(result, Ok(()));
+
+    let written = String::from_utf8(buffer).unwrap();
+    let expected = concat!("{\n", "  \"ok\": true\n", "}");
+    assert_eq!(written.trim(), expected);
+  }
+
+  #[tokio::test]
+  async fn handle_when_delete_item_with_invalid_list_id_it_should_return_usage_error() {
+    let item_uuid = Uuid::parse_str("d3b07384-d113-40e1-a20c-55c3c0a4e70e").unwrap();
+    let mock_client = MockClient::default();
+
+    let command = ListsCommand::DeleteItem {
+      list_id: 0,
+      item_id: item_uuid,
+    };
+    let mut buffer = Vec::new();
+
+    let result = handle(&command, &mock_client, &mut buffer, false).await;
+
+    assert_eq!(
+      result,
+      Err(CliError::usage("list_id must be greater than 0."))
+    );
+    assert!(buffer.is_empty());
+  }
+
+  #[tokio::test]
+  async fn handle_when_delete_item_fails_it_should_return_mapped_cli_error() {
+    let item_uuid = Uuid::parse_str("d3b07384-d113-40e1-a20c-55c3c0a4e70e").unwrap();
+    let mock_client = MockClient {
+      delete_list_item_result: Err(OnspringError::Api {
+        status_code: 404,
+        message: "List item not found".to_string(),
+      }),
+      ..Default::default()
+    };
+
+    let command = ListsCommand::DeleteItem {
+      list_id: 1,
+      item_id: item_uuid,
+    };
+    let mut buffer = Vec::new();
+
+    let result = handle(&command, &mock_client, &mut buffer, false).await;
+
+    assert_eq!(
+      result,
+      Err(CliError::runtime(
+        "API request failed (404): List item not found"
+      ))
+    );
+    assert!(buffer.is_empty());
+  }
+}
+
diff --git a/src/commands/mod.rs b/src/commands/mod.rs
index 3ed5b31..dbdcac1 100644
--- a/src/commands/mod.rs
+++ b/src/commands/mod.rs
@@ -1,8 +1,9 @@
 pub mod apps;
 pub mod fields;
+pub mod files;
+pub mod lists;
 pub mod ping;
 pub mod records;
-pub mod files;
 
 use std::io::Write;
 
@@ -21,5 +22,6 @@ pub async fn handle<C: OnspringRunner, W: Write>(
     Command::Fields { command } => fields::handle(command, client, writer, cli.pretty).await,
     Command::Records { command } => records::handle(command, client, writer, cli.pretty).await,
     Command::Files { command } => files::handle(command, client, writer, cli.pretty).await,
-}
+    Command::Lists { command } => lists::handle(command, client, writer, cli.pretty).await,
+  }
 }
diff --git a/src/output.rs b/src/output.rs
index 78d4639..46c0b65 100644
--- a/src/output.rs
+++ b/src/output.rs
@@ -3,8 +3,8 @@ use std::io::Write;
 use chrono::{DateTime, Utc};
 use onspring::{
   App, CollectionResponse, CreatedWithIdResponse, Field, FileInfo, FormulaOutputType,
-  ListFieldValue, Multiplicity, PagedResponse, Record, RecordFieldValue, SaveRecordResponse,
-  ValueType,
+  ListFieldValue, Multiplicity, PagedResponse, Record, RecordFieldValue, SaveListItemResponse,
+  SaveRecordResponse, ValueType,
 };
 use serde::Serialize;
 use uuid::Uuid;
@@ -251,6 +251,18 @@ impl From<CreatedWithIdResponse> for CreatedWithIdResponseOutput {
   }
 }
 
+#[derive(Debug, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SaveListItemResponseOutput {
+  pub id: Uuid,
+}
+
+impl From<SaveListItemResponse> for SaveListItemResponseOutput {
+  fn from(value: SaveListItemResponse) -> Self {
+    Self { id: value.id }
+  }
+}
+
 pub fn render_json<T: Serialize>(value: &T, pretty: bool) -> CliResult<String> {
   if pretty {
     serde_json::to_string_pretty(value).map_err(|_| CliError::runtime("Failed to serialize output"))