Oumi is an entirely open-source platform that enhances the complete lifecycle of foundation models, encompassing everything from data preparation and training to evaluation and deployment. It facilitates the training and fine-tuning of models with parameter counts ranging from 10 million to an impressive 405 billion, utilizing cutting-edge methodologies such as SFT, LoRA, QLoRA, and DPO. Supporting both text-based and multimodal models, Oumi is compatible with various architectures like Llama, DeepSeek, Qwen, and Phi. The platform also includes tools for data synthesis and curation, allowing users to efficiently create and manage their training datasets. For deployment, Oumi seamlessly integrates with well-known inference engines such as vLLM and SGLang, which optimizes model serving. Additionally, it features thorough evaluation tools across standard benchmarks to accurately measure model performance. Oumi's design prioritizes flexibility, enabling it to operate in diverse environments ranging from personal laptops to powerful cloud solutions like AWS, Azure, GCP, and Lambda, making it a versatile choice for developers. This adaptability ensures that users can leverage the platform regardless of their operational context, enhancing its appeal across different use cases.