A basic Flask application requires creating a Flask instance and defining routes:

from flask import Flask

app = Flask(__name__)

@app.route('/')
def hello_world():
    return 'Hello, World!'

if __name__ == '__main__':
    app.run(debug=True)

The Flask(__name__) creates the application instance, @app.route() decorator defines URL endpoints, and app.run() starts the development server.