Mem0 (pronounced 'mem-zero') is an intelligent memory layer for AI applications and agents. It enables personalized AI interactions by remembering user preferences, adapting to individual needs, and continuously learning over time. Mem0 implements a hierarchical memory system with four distinct levels: User Memory for individual preferences and conversation history, Session Memory for single-conversation context, Agent Memory for task retention and learned behaviors, and Organization Memory for shared knowledge across teams. The platform delivers 26% higher accuracy than OpenAI Memory on benchmarks, 91% faster responses than full-context approaches, and 90% lower token usage. Its memory compression engine intelligently compresses chat history into optimized representations, achieving up to 80% prompt token reduction. Graph memory (available on Pro and above) provides a knowledge graph linking entities and relationships across conversations. Mem0 is model-agnostic, compatible with OpenAI, Anthropic, and open-source LLMs, and integrates with frameworks like LangChain and LlamaIndex. The open-source project has surpassed 41,000 GitHub stars and recorded over 13 million Python package downloads. Backed by Y Combinator with a $24M Series A, Mem0 processed over 186 million API calls in Q3 2025.