What are the major LLM providers in 2026?

The major closed-source LLM providers in 2026 are OpenAI with GPT and o-series, Anthropic with Claude, Google with Gemini, and to a lesser extent xAI with Grok. The major open-source families are Meta Llama, Mistral, Qwen from Alibaba, DeepSeek, and Microsoft Phi. Most production systems use a mix depending on task, cost, and quality requirements.