Learn Prompting (learnprompting.org) is the world's largest free, open-source course and resource hub for prompt engineering and effective AI communication in 2026. It offers beginner-to-advanced guides, structured courses (e.g., ChatGPT for Everyone, Advanced Prompt Engineering), research-backed techniques, and specialized masterclasses on AI security/red-teaming. With 3M+ learners, multilingual support, a massive Discord community, and free core content (paid on-demand/live options), it's the go-to platform for mastering LLMs like ChatGPT, Claude, and Gemini.