cyberbotics/webots
Webots is an open-source robot simulator for modeling, programming, and simulating robots, vehicles, and mechanical systems.

Webots is a professional robot simulation platform that provides a complete development environment for modeling and simulating robotic systems. It supports physics-based simulation of robots and vehicles, sensor simulation including cameras and lidars, and integrates with ROS and ROS2 for robotics workflows. While primarily a simulation tool, it is widely used for training and evaluating autonomous systems including reinforcement learning agents, autonomous vehicles, and computer-vision pipelines.