GitHub Actions is GitHub's CI/CD and automation platform built directly into repositories, enabling workflows to run on code events, schedules, or manual triggers. It eliminates external CI/CD dependencies by providing hosted runners, a marketplace of pre-built actions, and flexible YAML-based workflow definitions. The platform scales from simple automated testing to complex deployment pipelines with matrix builds, reusable workflows, and fine-grained security controls—making it the de facto automation solution for projects hosted on GitHub.