diff --git a/app/commands.js b/app/commands.js
index d3562b7..18f8116 100644
--- a/app/commands.js
+++ b/app/commands.js
@@ -4,15 +4,19 @@ import { ReopenCommand } from "./commands/reopen-command.js";
 import { LabelCommand } from "./commands/label-command.js";
 import { RemoveLabelCommand } from "./commands/remove-label-command.js";
 import { ReviewerCommand } from "./commands/reviewer-command.js";
+import { HelpCommand } from "./commands/help-command.js";
+
+export const ALL_COMMANDS = [
+  TransferCommand,
+  CloseCommand,
+  ReopenCommand,
+  LabelCommand,
+  RemoveLabelCommand,
+  ReviewerCommand,
+  HelpCommand,
+];
 
 export function getCommands(id, payload) {
-  const commands = [
-    new TransferCommand(id, payload),
-    new CloseCommand(id, payload),
-    new ReopenCommand(id, payload),
-    new LabelCommand(id, payload),
-    new RemoveLabelCommand(id, payload),
-    new ReviewerCommand(id, payload),
-  ];
+  const commands = ALL_COMMANDS.map((Cls) => new Cls(id, payload));
   return commands.filter((command) => command.matches());
 }
diff --git a/app/commands.test.js b/app/commands.test.js
index 3e9ef17..675d640 100644
--- a/app/commands.test.js
+++ b/app/commands.test.js
@@ -29,4 +29,14 @@ describe("commands", () => {
 
     expect(commands).toHaveLength(2);
   });
+
+  test("getCommands matches /help command", () => {
+    const commands = getCommands("any", {
+      comment: {
+        body: "/help",
+      },
+    });
+
+    expect(commands).toHaveLength(1);
+  });
 });
diff --git a/app/commands/close-command.js b/app/commands/close-command.js
index d9d0c4a..35aea9b 100644
--- a/app/commands/close-command.js
+++ b/app/commands/close-command.js
@@ -12,10 +12,20 @@ import {
 const classLogger = getLogger("commands/close-command");
 
 export class CloseCommand extends Command {
+  static configKey = "close";
+
   constructor(id, payload) {
     super(id, payload);
   }
 
+  get usage() {
+    return "/close [not-planned]";
+  }
+
+  get description() {
+    return "Close this issue";
+  }
+
   matches() {
     return closeMatcher(extractBody(this.payload));
   }
diff --git a/app/commands/command.js b/app/commands/command.js
index 988b480..05fb99b 100644
--- a/app/commands/command.js
+++ b/app/commands/command.js
@@ -4,6 +4,14 @@ export class Command {
     this.payload = payload;
   }
 
+  get usage() {
+    throw new Error("usage must be implemented");
+  }
+
+  get description() {
+    throw new Error("description must be implemented");
+  }
+
   matches() {
     throw new Error("matches() must be implemented");
   }
diff --git a/app/commands/help-command.js b/app/commands/help-command.js
new file mode 100644
index 0000000..bce61fe
--- /dev/null
+++ b/app/commands/help-command.js
@@ -0,0 +1,68 @@
+import { helpMatcher } from "../matchers.js";
+import { reportError } from "../github.js";
+import { Command } from "./command.js";
+import { getLogger } from "../logger.js";
+import {
+  extractBody,
+  extractHtmlUrl,
+  extractLabelableId,
+} from "../comment-extractor.js";
+import { ALL_COMMANDS } from "../commands.js";
+
+const classLogger = getLogger("commands/help-command");
+
+function buildHelpText(config) {
+  const rows = ALL_COMMANDS.filter(
+    (Cls) => !Cls.configKey || config.commands[Cls.configKey]?.enabled,
+  )
+    .map(
+      (Cls) => `| \`${Cls.prototype.usage}\` | ${Cls.prototype.description} |`,
+    )
+    .join("\n");
+
+  return `### Available Commands\n\n| Command | Description |\n| ------- | ----------- |\n${rows}`;
+}
+
+export class HelpCommand extends Command {
+  get usage() {
+    return "/help";
+  }
+
+  get description() {
+    return "Show available commands";
+  }
+
+  matches() {
+    return helpMatcher(extractBody(this.payload));
+  }
+
+  enabled(config) {
+    this._config = config;
+    return {
+      enabled: true,
+    };
+  }
+
+  async run(authToken) {
+    const logger = classLogger.child({
+      user: this.payload.sender.login,
+      id: this.id,
+    });
+
+    logger.info(`Showing help for ${extractHtmlUrl(this.payload)}`);
+    try {
+      await reportError(
+        authToken,
+        extractLabelableId(this.payload),
+        buildHelpText(this._config),
+      );
+    } catch (error) {
+      logger.error(
+        `Failed to post help comment ${
+          error.errors ? JSON.stringify(error.errors) : ""
+        }`,
+        error,
+      );
+    }
+  }
+}
diff --git a/app/commands/label-command.js b/app/commands/label-command.js
index 3737eb5..c1ad4ab 100644
--- a/app/commands/label-command.js
+++ b/app/commands/label-command.js
@@ -14,10 +14,20 @@ import {
 const classLogger = getLogger("commands/label-command");
 
 export class LabelCommand extends Command {
+  static configKey = "label";
+
   constructor(id, payload) {
     super(id, payload);
   }
 
+  get usage() {
+    return "/label <label1,label2>";
+  }
+
+  get description() {
+    return "Add labels to this issue or pull request";
+  }
+
   matches() {
     return labelMatcher(extractBody(this.payload));
   }
diff --git a/app/commands/remove-label-command.js b/app/commands/remove-label-command.js
index 9b09517..ea39d4c 100644
--- a/app/commands/remove-label-command.js
+++ b/app/commands/remove-label-command.js
@@ -13,10 +13,20 @@ import {
 const classLogger = getLogger("commands/remove-label-command");
 
 export class RemoveLabelCommand extends Command {
+  static configKey = "removeLabel";
+
   constructor(id, payload) {
     super(id, payload);
   }
 
+  get usage() {
+    return "/remove-label <label1,label2>";
+  }
+
+  get description() {
+    return "Remove labels from this issue or pull request";
+  }
+
   matches() {
     return removeLabelMatcher(extractBody(this.payload));
   }
diff --git a/app/commands/reopen-command.js b/app/commands/reopen-command.js
index 728a19e..965abbd 100644
--- a/app/commands/reopen-command.js
+++ b/app/commands/reopen-command.js
@@ -12,10 +12,20 @@ import {
 const classLogger = getLogger("commands/reopen-command");
 
 export class ReopenCommand extends Command {
+  static configKey = "reopen";
+
   constructor(id, payload) {
     super(id, payload);
   }
 
+  get usage() {
+    return "/reopen";
+  }
+
+  get description() {
+    return "Reopen this issue";
+  }
+
   matches() {
     return reopenMatcher(extractBody(this.payload));
   }
diff --git a/app/commands/reviewer-command.js b/app/commands/reviewer-command.js
index 952a119..49d2cbf 100644
--- a/app/commands/reviewer-command.js
+++ b/app/commands/reviewer-command.js
@@ -13,10 +13,20 @@ import {
 const classLogger = getLogger("commands/reviewer-command");
 
 export class ReviewerCommand extends Command {
+  static configKey = "reviewer";
+
   constructor(id, payload) {
     super(id, payload);
   }
 
+  get usage() {
+    return "/reviewer <reviewer1,reviewer2>";
+  }
+
+  get description() {
+    return "Request reviewers for this pull request";
+  }
+
   matches() {
     return reviewerMatcher(extractBody(this.payload));
   }
diff --git a/app/commands/transfer-command.js b/app/commands/transfer-command.js
index 18cd95f..e74c0f5 100644
--- a/app/commands/transfer-command.js
+++ b/app/commands/transfer-command.js
@@ -12,10 +12,20 @@ import {
 const classLogger = getLogger("commands/transfer-command");
 
 export class TransferCommand extends Command {
+  static configKey = "transfer";
+
   constructor(id, payload) {
     super(id, payload);
   }
 
+  get usage() {
+    return "/transfer <repo-name>";
+  }
+
+  get description() {
+    return "Transfer this issue to another repository";
+  }
+
   matches() {
     return transferMatcher(extractBody(this.payload));
   }
diff --git a/app/matchers.js b/app/matchers.js
index 2c9fab7..d88945c 100644
--- a/app/matchers.js
+++ b/app/matchers.js
@@ -24,3 +24,7 @@ export function removeLabelMatcher(text) {
 export function reviewerMatcher(text) {
   return text.match(/(?:^| | \r\n|\n)\/reviewers? ([ /@A-Za-z\d-,]+)/);
 }
+
+export function helpMatcher(text) {
+  return text.match(/(?:^| | \r\n|\n)\/help/);
+}
diff --git a/app/matchers.test.js b/app/matchers.test.js
index d0a9031..22fa19c 100644
--- a/app/matchers.test.js
+++ b/app/matchers.test.js
@@ -1,5 +1,6 @@
 import {
   closeMatcher,
+  helpMatcher,
   labelMatcher,
   removeLabelMatcher,
   reopenMatcher,
@@ -240,4 +241,27 @@ describe("matchers", () => {
       expect(result).toBeFalsy();
     });
   });
+
+  describe("help", () => {
+    test("matches /help", () => {
+      const result = helpMatcher("/help");
+
+      expect(result).toBeTruthy();
+    });
+    test("does not match input without /help", () => {
+      const result = helpMatcher("help");
+
+      expect(result).toBeFalsy();
+    });
+    test("does not match in the middle of a string", () => {
+      const result = helpMatcher("something/help");
+
+      expect(result).toBeFalsy();
+    });
+    test("matches /help at the start of a new line", () => {
+      const result = helpMatcher("some text\n/help");
+
+      expect(result).toBeTruthy();
+    });
+  });
 });