Bazel is a free and open-source software tool used for the automation of building and testing software. Google uses the build tool Blaze internally and released an open-source port of the Blaze tool as Bazel, named as an anagram of Blaze. Bazel was first released in March 2015 and entered beta by September 2015.

Bazel was designed to be able to scale to Google's needs and meet Google's requirements of reproducibility and platform/language support. All software at Google is built using Bazel. Google uses Bazel and its rules for millions of builds every day.