Sierra

Sierra is an Enterprise Voice Agents company founded in 2023 and based in San Francisco, United States. It has raised $1.6B in total funding, most recently a Series D in 2026 at a $15.8B valuation.

Sierra builds conversational AI agents for enterprise customer-experience workflows, replacing tier-1 support teams. Founded by Bret Taylor (ex-Salesforce co-CEO) and Clay Bavor (ex-Google Labs); customers include ADT, SiriusXM, and OluKai.

Sierra hit $100M ARR in seven quarters and achieved a $15B valuation, the fastest enterprise-AI revenue ramp on record.

sierra.ai Enterprise Voice Agents

United Statesprivate

At a glance

Total raised

$1.6B

last round series d

Headcount

501-1k

approximate · public range

Headquarters

San Francisco

United States

Founded

2023

3 years active

Status

Private

Enterprise Voice Agents

Latest valuation

Funding history

Total raised

$1.6B

Rounds tracked

Latest stage

Series D

Latest valuation

$15.8B

Date	Stage	Amount	Valuation	Lead investors
May 4, 2026	Series D	$950M	$15.8B	Tiger Global, GV
Sep 4, 2025	Series C	$350M	$10B

Sierra

At a glance

Funding history

In the news

Sierra AI review: the enterprise CX agent platform explained

Kraken Launches Autonomous Agents for Utility Customer Service Built in Partnership with Sierra

Kraken launches autonomous agents for utility customer service built in partnership with Sierra

OpenAI chair's AI startup Sierra raises $950M at over $15B valuation

Watch

Leadership

Products

Sierra AI Agent Platform

Agent Studio 2.0

Ghostwriter

Most recent patents

Open roles

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