Brian Alexander Wecht, also known by his character name Ninja Brian, is an American musician, Internet personality, podcaster, and theoretical physicist. He is best known as a member of comedy musical duo Ninja Sex Party and video game-based comedy music trio Starbomb. He has also appeared on the Let's Play webseries Game Grumps, all three alongside Dan Avidan.

Wecht originally worked as a theoretical physicist, and notably held research positions at Harvard University, the Massachusetts Institute of Technology, the Institute for Advanced Study, the University of Michigan, and the Queen Mary University of London. Specialized in particle physics, his work included research on string theory, supersymmetry, and quantum field theory. He retired in 2015, choosing to join Game Grumps while focusing on his musical career. He is also the co-creator of The Story Collider, a science-based story telling podcast recorded in front of a live audience.

In Ninja Sex Party, Wecht plays the character of "Ninja Brian", a non-verbal, homicidal masked ninja, in both live shows and music videos. He performed all instruments on early Ninja Sex Party albums, until TWRP started acting as their backing band in 2015. Wecht also co-hosts the podcast Leighton Night with Brian Wecht and portrays Ninja Brian on his live comedy show titled Ninja Brian's All-Star Variety Luau Spectacular.

Wecht attended Williams College and the University of California, San Diego where he obtained his PhD in particle physics in 2004. Wecht held research positions at Harvard University, the Center for Theoretical Physics at the Massachusetts Institute of Technology, the Institute for Advanced Study, and the University of Michigan, prior to becoming a faculty member at the Queen Mary University of London. While there, Wecht worked on string theory, supersymmetry, and quantum field theory.

Wecht has an extensive record of highly cited contributions. He retired in 2015 to join Game Grumps and dedicate himself to his music career.^{[failed verification]}

Prior to meeting Dan Avidan, Wecht was the musical director of an improv comedy troupe in New York. In 2009, Avidan, who had conceptualized Ninja Sex Party and was in search of a bandmate and/or producer, was introduced to Wecht by Julie Katz, a member of Wecht's comedy troupe (who would later be featured in Ninja Sex Party's music video "The Decision"), to whom Avidan had asked if she knew any musicians.

Specializing in humorous songs, both on stage or in their music videos, the duo started by appearing on various film festivals. They regularly published original songs on their YouTube channel, which progressively helped them in becoming popular, as well as studio albums on a regular basis. Although he only played keyboards on stage, Wecht performed all instruments on early Ninja Sex Party albums, including piano and drum machines, while Avidan was in charge of all vocals, except for occasional backing or spoken vocals by Wecht. Ultimately, the duo was joined by backing band TWRP in 2015, after which Wecht focused solely on keyboards for studio recordings.

Wecht's bandmate Dan Avidan had been the co-host of the Let's Play webseries Game Grumps since 2013. The same year, Wecht, Avidan, and Avidan's Game Grumps co-host Arin Hanson formed Starbomb. This new comedy band followed the humorous style of Ninja Sex Party, but focused on video game parodies. The project was officially revealed on December 3, 2013. It was quickly followed by a self-titled album on December 17. A second album, Player Select, was released on December 16, 2014, followed by Starbomb's third album, The TryForce, was released on April 19, 2019. Their fourth album "Starbomb Boom: Rise of Lyrics" was released on October 24, 2024.