Sierra Raises $950M at $15.8B Valuation for Enterprise AI Agent Platform
Tags AI · Enterprise · Infrastructure
Sierra, the enterprise AI agent platform founded by Bret Taylor, raised $950M in a Series E round led by Tiger Global and GV (Google Ventures) at a $15.8B post-money valuation. The company crossed $150M ARR in February 2026 and serves more than 40% of the Fortune 50. Sierra launched Ghostwriter, an agent-as-a-service platform for building AI agents from natural-language prompts. The round was part of a broader $17B week in AI funding that also included Ramp ($750M), Moonshot AI ($2B), and ElevenLabs ($550M).
Technical significance
Sierra's $15.8B valuation on $150M ARR (roughly 100x multiple) reflects extreme investor confidence in the enterprise AI agent market. The fact that 40% of Fortune 50 companies are already Sierra customers suggests enterprise AI agent adoption has crossed the early-adopter threshold. The $17B week in AI funding indicates that capital continues to flow aggressively into AI agent infrastructure.