diff --git a/.cspell/code-terms.txt b/.cspell/code-terms.txt
index 8b549f888..710020c52 100644
--- a/.cspell/code-terms.txt
+++ b/.cspell/code-terms.txt
@@ -143,6 +143,7 @@ typeof
 typestr
 unshift
 urlsafe
+usecase
 verifymethod
 VERIFYMTHD
 WARN_DOCSDIR_DOESNT_MATCH
diff --git a/packages/mermaid/src/diagram-api/diagram-orchestration.ts b/packages/mermaid/src/diagram-api/diagram-orchestration.ts
index 97b9852ff..fab00bd3c 100644
--- a/packages/mermaid/src/diagram-api/diagram-orchestration.ts
+++ b/packages/mermaid/src/diagram-api/diagram-orchestration.ts
@@ -28,6 +28,7 @@ import architecture from '../diagrams/architecture/architectureDetector.js';
 import { registerLazyLoadedDiagrams } from './detectType.js';
 import { registerDiagram } from './diagramAPI.js';
 import { treemap } from '../diagrams/treemap/detector.js';
+import { usecase } from '../diagrams/usecase/detector.js';
 import '../type.d.ts';
 
 let hasLoadedDiagrams = false;
@@ -101,6 +102,7 @@ export const addDiagrams = () => {
     xychart,
     block,
     radar,
-    treemap
+    treemap,
+    usecase
   );
 };
diff --git a/packages/mermaid/src/diagrams/usecase/db.ts b/packages/mermaid/src/diagrams/usecase/db.ts
new file mode 100644
index 000000000..42e8e7135
--- /dev/null
+++ b/packages/mermaid/src/diagrams/usecase/db.ts
@@ -0,0 +1,38 @@
+import type { DiagramDB } from '../../diagram-api/types.js';
+import type { UsecaseDiagramConfig, UsecaseNode } from './types.js';
+import { cleanAndMerge } from '../../utils.js';
+
+export class UsecaseDiagramDB implements DiagramDB {
+  public getNodes() {
+    return [];
+  }
+
+  public getConfig() {
+    return cleanAndMerge({}) as Required<UsecaseDiagramConfig>;
+  }
+
+  public addNode(node: UsecaseNode, level: number) {
+    if (level === 0) {
+      // TODO
+    }
+  }
+
+  public getRoot() {
+    return { name: '', children: [] };
+  }
+
+  public addClass(_id: string, _style: string) {
+    // TODO
+  }
+  public getClasses() {
+    // TODO
+  }
+
+  public getStylesForClass(_classSelector: string) {
+    // TODO
+  }
+
+  public clear() {
+    // commonClear();
+  }
+}
diff --git a/packages/mermaid/src/diagrams/usecase/detector.ts b/packages/mermaid/src/diagrams/usecase/detector.ts
new file mode 100644
index 000000000..71b58bef6
--- /dev/null
+++ b/packages/mermaid/src/diagrams/usecase/detector.ts
@@ -0,0 +1,22 @@
+import type {
+  DiagramDetector,
+  DiagramLoader,
+  ExternalDiagramDefinition,
+} from '../../diagram-api/types.js';
+
+const id = 'usecase';
+
+const detector: DiagramDetector = (txt) => {
+  return /^\s*usecase/.test(txt);
+};
+
+const loader: DiagramLoader = async () => {
+  const { diagram } = await import('./diagram.js');
+  return { id, diagram };
+};
+
+export const usecase: ExternalDiagramDefinition = {
+  id,
+  detector,
+  loader,
+};
diff --git a/packages/mermaid/src/diagrams/usecase/diagram.ts b/packages/mermaid/src/diagrams/usecase/diagram.ts
new file mode 100644
index 000000000..507273e36
--- /dev/null
+++ b/packages/mermaid/src/diagrams/usecase/diagram.ts
@@ -0,0 +1,14 @@
+import type { DiagramDefinition } from '../../diagram-api/types.js';
+import { UsecaseDiagramDB } from './db.js';
+import { parser } from './parser.js';
+import { renderer } from './renderer.js';
+import styles from './styles.js';
+
+export const diagram: DiagramDefinition = {
+  parser,
+  get db() {
+    return new UsecaseDiagramDB();
+  },
+  renderer,
+  styles,
+};
diff --git a/packages/mermaid/src/diagrams/usecase/parser.ts b/packages/mermaid/src/diagrams/usecase/parser.ts
new file mode 100644
index 000000000..e679c8ae7
--- /dev/null
+++ b/packages/mermaid/src/diagrams/usecase/parser.ts
@@ -0,0 +1,40 @@
+import { parse } from '@mermaid-js/parser';
+import type { ParserDefinition } from '../../diagram-api/types.js';
+import { log } from '../../logger.js';
+import { populateCommonDb } from '../common/populateCommonDb.js';
+import type { UsecaseAst } from './types.js';
+import { UsecaseDiagramDB } from './db.js';
+
+/**
+ * Populates the database with data from the Usecase AST
+ * @param ast - The Usecase AST
+ */
+const populate = (ast: UsecaseAst, db: UsecaseDiagramDB) => {
+  // We need to bypass the type checking for populateCommonDb
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  populateCommonDb(ast as any, db);
+};
+
+export const parser: ParserDefinition = {
+  // @ts-expect-error - UsecaseDB is not assignable to DiagramDB
+  parser: { yy: undefined },
+  parse: async (text: string): Promise<void> => {
+    try {
+      // Use a generic parse that accepts any diagram type
+
+      const parseFunc = parse as (diagramType: string, text: string) => Promise<UsecaseAst>;
+      const ast = await parseFunc('usecase', text);
+      log.debug('Usecase AST:', ast);
+      const db = parser.parser?.yy;
+      if (!(db instanceof UsecaseDiagramDB)) {
+        throw new Error(
+          'parser.parser?.yy was not a UsecaseDiagramDB. This is due to a bug within Mermaid, please report this issue at https://github.com/mermaid-js/mermaid/issues.'
+        );
+      }
+      populate(ast, db);
+    } catch (error) {
+      log.error('Error parsing usecase:', error);
+      throw error;
+    }
+  },
+};
diff --git a/packages/mermaid/src/diagrams/usecase/renderer.ts b/packages/mermaid/src/diagrams/usecase/renderer.ts
new file mode 100644
index 000000000..6f6b5305f
--- /dev/null
+++ b/packages/mermaid/src/diagrams/usecase/renderer.ts
@@ -0,0 +1,21 @@
+import type { Diagram } from '../../Diagram.js';
+import type {
+  DiagramRenderer,
+  DiagramStyleClassDef,
+  DrawDefinition,
+} from '../../diagram-api/types.js';
+
+/**
+ * Draws the Usecase diagram
+ */
+const draw: DrawDefinition = (_text, _id, _version, _diagram: Diagram) => {
+  // TODO: Implement the draw function for the usecase diagram
+};
+
+const getClasses = function (
+  _text: string,
+  _diagramObj: Pick<Diagram, 'db'>
+): Map<string, DiagramStyleClassDef> {
+  return new Map<string, DiagramStyleClassDef>();
+};
+export const renderer: DiagramRenderer = { draw, getClasses };
diff --git a/packages/mermaid/src/diagrams/usecase/styles.ts b/packages/mermaid/src/diagrams/usecase/styles.ts
new file mode 100644
index 000000000..9593a6296
--- /dev/null
+++ b/packages/mermaid/src/diagrams/usecase/styles.ts
@@ -0,0 +1,51 @@
+import type { DiagramStylesProvider } from '../../diagram-api/types.js';
+import { cleanAndMerge } from '../../utils.js';
+import type { UsecaseStyleOptions } from './types.js';
+
+const defaultUsecaseStyleOptions: UsecaseStyleOptions = {
+  sectionStrokeColor: 'black',
+  sectionStrokeWidth: '1',
+  sectionFillColor: '#efefef',
+  leafStrokeColor: 'black',
+  leafStrokeWidth: '1',
+  leafFillColor: '#efefef',
+  labelColor: 'black',
+  labelFontSize: '12px',
+  valueFontSize: '10px',
+  valueColor: 'black',
+  titleColor: 'black',
+  titleFontSize: '14px',
+};
+
+export const getStyles: DiagramStylesProvider = ({
+  usecase,
+}: { usecase?: UsecaseStyleOptions } = {}) => {
+  const options = cleanAndMerge(defaultUsecaseStyleOptions, usecase);
+
+  return `
+  .usecaseNode.section {
+    stroke: ${options.sectionStrokeColor};
+    stroke-width: ${options.sectionStrokeWidth};
+    fill: ${options.sectionFillColor};
+  }
+  .usecaseNode.leaf {
+    stroke: ${options.leafStrokeColor};
+    stroke-width: ${options.leafStrokeWidth};
+    fill: ${options.leafFillColor};
+  }
+  .usecaseLabel {
+    fill: ${options.labelColor};
+    font-size: ${options.labelFontSize};
+  }
+  .usecaseValue {
+    fill: ${options.valueColor};
+    font-size: ${options.valueFontSize};
+  }
+  .usecaseTitle {
+    fill: ${options.titleColor};
+    font-size: ${options.titleFontSize};
+  }
+  `;
+};
+
+export default getStyles;
diff --git a/packages/mermaid/src/diagrams/usecase/types.ts b/packages/mermaid/src/diagrams/usecase/types.ts
new file mode 100644
index 000000000..977dca8d5
--- /dev/null
+++ b/packages/mermaid/src/diagrams/usecase/types.ts
@@ -0,0 +1,68 @@
+import type { DiagramDBBase, DiagramStyleClassDef } from '../../diagram-api/types.js';
+import type { BaseDiagramConfig } from '../../config.type.js';
+
+export interface UsecaseNode {
+  name: string;
+  children?: UsecaseNode[];
+  value?: number;
+  parent?: UsecaseNode;
+  classSelector?: string;
+  cssCompiledStyles?: string[];
+}
+
+export interface UsecaseDiagramDB extends DiagramDBBase<UsecaseDiagramConfig> {
+  getNodes: () => UsecaseNode[];
+  addNode: (node: UsecaseNode, level: number) => void;
+  getRoot: () => UsecaseNode | undefined;
+  getClasses: () => Map<string, DiagramStyleClassDef>;
+  addClass: (className: string, style: string) => void;
+  getStylesForClass: (classSelector: string) => string[];
+  // Update
+}
+
+export interface UsecaseStyleOptions {
+  sectionStrokeColor?: string;
+  sectionStrokeWidth?: string;
+  sectionFillColor?: string;
+  leafStrokeColor?: string;
+  leafStrokeWidth?: string;
+  leafFillColor?: string;
+  labelColor?: string;
+  labelFontSize?: string;
+  valueFontSize?: string;
+  valueColor?: string;
+  titleColor?: string;
+  titleFontSize?: string;
+}
+
+export interface UsecaseData {
+  nodes: UsecaseNode[];
+  levels: Map<UsecaseNode, number>;
+  root?: UsecaseNode;
+  outerNodes: UsecaseNode[];
+}
+
+export interface UsecaseItem {
+  $type: string;
+  name: string;
+  value?: number;
+  classSelector?: string;
+}
+
+export interface UsecaseAst {
+  title?: string;
+  description?: string;
+}
+
+// Define the UsecaseDiagramConfig interface
+export interface UsecaseDiagramConfig extends BaseDiagramConfig {
+  padding?: number;
+  diagramPadding?: number;
+  showValues?: boolean;
+  nodeWidth?: number;
+  nodeHeight?: number;
+  borderWidth?: number;
+  valueFontSize?: number;
+  labelFontSize?: number;
+  valueFormat?: string;
+}
diff --git a/packages/parser/langium-config.json b/packages/parser/langium-config.json
index 85c722a02..cec3cc2cd 100644
--- a/packages/parser/langium-config.json
+++ b/packages/parser/langium-config.json
@@ -35,6 +35,11 @@
       "id": "treemap",
       "grammar": "src/language/treemap/treemap.langium",
       "fileExtensions": [".mmd", ".mermaid"]
+    },
+    {
+      "id": "usecase",
+      "grammar": "src/language/usecase/usecase.langium",
+      "fileExtensions": [".mmd", ".mermaid"]
     }
   ],
   "mode": "production",
diff --git a/packages/parser/src/language/index.ts b/packages/parser/src/language/index.ts
index 9b31af5ba..89bfc15da 100644
--- a/packages/parser/src/language/index.ts
+++ b/packages/parser/src/language/index.ts
@@ -9,6 +9,7 @@ export {
   GitGraph,
   Radar,
   Treemap,
+  Usecase,
   Branch,
   Commit,
   Merge,
@@ -24,6 +25,7 @@ export {
   isBranch,
   isCommit,
   isMerge,
+  isUsecase,
 } from './generated/ast.js';
 
 export {
@@ -35,6 +37,7 @@ export {
   GitGraphGeneratedModule,
   RadarGeneratedModule,
   TreemapGeneratedModule,
+  UsecaseGeneratedModule,
 } from './generated/module.js';
 
 export * from './gitGraph/index.js';
@@ -45,3 +48,4 @@ export * from './pie/index.js';
 export * from './architecture/index.js';
 export * from './radar/index.js';
 export * from './treemap/index.js';
+export * from './usecase/index.js';
diff --git a/packages/parser/src/language/usecase/index.ts b/packages/parser/src/language/usecase/index.ts
new file mode 100644
index 000000000..fd3c604b0
--- /dev/null
+++ b/packages/parser/src/language/usecase/index.ts
@@ -0,0 +1 @@
+export * from './module.js';
diff --git a/packages/parser/src/language/usecase/module.ts b/packages/parser/src/language/usecase/module.ts
new file mode 100644
index 000000000..156eac759
--- /dev/null
+++ b/packages/parser/src/language/usecase/module.ts
@@ -0,0 +1,35 @@
+import { type DefaultSharedCoreModuleContext, type LangiumCoreServices } from 'langium';
+import type { Module, PartialLangiumCoreServices } from 'langium';
+import { EmptyFileSystem } from 'langium';
+import { UsecaseTokenBuilder } from './tokenBuilder.js';
+import { UsecaseValueConverter } from './valueConverter.js';
+import { UsecaseValidator } from './usecase-validator.js';
+
+interface UsecaseAddedServices {
+  parser: {
+    TokenBuilder: UsecaseTokenBuilder;
+    ValueConverter: UsecaseValueConverter;
+  };
+  validation: {
+    UsecaseValidator: UsecaseValidator;
+  };
+}
+
+export type UsecaseServices = LangiumCoreServices & UsecaseAddedServices;
+
+export const UsecaseModule: Module<
+  UsecaseServices,
+  PartialLangiumCoreServices & UsecaseAddedServices
+> = {
+  parser: {
+    TokenBuilder: () => new UsecaseTokenBuilder(),
+    ValueConverter: () => new UsecaseValueConverter(),
+  },
+  validation: {
+    UsecaseValidator: () => new UsecaseValidator(),
+  },
+};
+
+export function createUsecaseServices(_context: DefaultSharedCoreModuleContext = EmptyFileSystem) {
+  // TODO
+}
diff --git a/packages/parser/src/language/usecase/tokenBuilder.ts b/packages/parser/src/language/usecase/tokenBuilder.ts
new file mode 100644
index 000000000..cf861374b
--- /dev/null
+++ b/packages/parser/src/language/usecase/tokenBuilder.ts
@@ -0,0 +1,7 @@
+import { AbstractMermaidTokenBuilder } from '../common/index.js';
+
+export class UsecaseTokenBuilder extends AbstractMermaidTokenBuilder {
+  public constructor() {
+    super(['usecase']);
+  }
+}
diff --git a/packages/parser/src/language/usecase/usecase-validator.ts b/packages/parser/src/language/usecase/usecase-validator.ts
new file mode 100644
index 000000000..5d14b46c2
--- /dev/null
+++ b/packages/parser/src/language/usecase/usecase-validator.ts
@@ -0,0 +1,12 @@
+import type { UsecaseServices } from './module.js';
+/**
+ * Register custom validation checks.
+ */
+export function registerValidationChecks(_services: UsecaseServices) {
+  // TODO
+}
+
+/**
+ * Implementation of custom validations.
+ */
+export class UsecaseValidator {}
diff --git a/packages/parser/src/language/usecase/usecase.langium b/packages/parser/src/language/usecase/usecase.langium
new file mode 100644
index 000000000..0ffdd02fc
--- /dev/null
+++ b/packages/parser/src/language/usecase/usecase.langium
@@ -0,0 +1 @@
+// TODO
\ No newline at end of file
diff --git a/packages/parser/src/language/usecase/valueConverter.ts b/packages/parser/src/language/usecase/valueConverter.ts
new file mode 100644
index 000000000..af5ab2af4
--- /dev/null
+++ b/packages/parser/src/language/usecase/valueConverter.ts
@@ -0,0 +1,12 @@
+import type { CstNode, GrammarAST, ValueType } from 'langium';
+import { AbstractMermaidValueConverter } from '../common/index.js';
+
+export class UsecaseValueConverter extends AbstractMermaidValueConverter {
+  protected runCustomConverter(
+    _rule: GrammarAST.AbstractRule,
+    _input: string,
+    _cstNode: CstNode
+  ): ValueType | undefined {
+    return undefined;
+  }
+}
diff --git a/packages/parser/src/parse.ts b/packages/parser/src/parse.ts
index 6f5a94ce6..53d970e9b 100644
--- a/packages/parser/src/parse.ts
+++ b/packages/parser/src/parse.ts
@@ -1,6 +1,15 @@
 import type { LangiumParser, ParseResult } from 'langium';
 
-import type { Info, Packet, Pie, Architecture, GitGraph, Radar, Treemap } from './index.js';
+import type {
+  Info,
+  Packet,
+  Pie,
+  Architecture,
+  GitGraph,
+  Radar,
+  Treemap,
+  // Usecase,
+} from './index.js';
 
 export type DiagramAST = Info | Packet | Pie | Architecture | GitGraph | Radar;
 
@@ -41,6 +50,11 @@ const initializers = {
     const parser = createTreemapServices().Treemap.parser.LangiumParser;
     parsers.treemap = parser;
   },
+  // usecase: async () => {
+  //   const { createUsecaseServices } = await import('./language/usecase/index.js');
+  //   const parser = createUsecaseServices().Usecase.parser.LangiumParser;
+  //   parsers.usecase = parser;
+  // },
 } as const;
 
 export async function parse(diagramType: 'info', text: string): Promise<Info>;
@@ -50,6 +64,7 @@ export async function parse(diagramType: 'architecture', text: string): Promise<
 export async function parse(diagramType: 'gitGraph', text: string): Promise<GitGraph>;
 export async function parse(diagramType: 'radar', text: string): Promise<Radar>;
 export async function parse(diagramType: 'treemap', text: string): Promise<Treemap>;
+// export async function parse(diagramType: 'usecase', text: string): Promise<Usecase>;
 
 export async function parse<T extends DiagramAST>(
   diagramType: keyof typeof initializers,