What is the name of the Indian astrophysicist on The Big Bang Theory?

The Indian astrophysicist on The Big Bang Theory is Raj Koothrappali. His full name is Rajesh Ramayan Koothrappali, and he is portrayed by British-Indian actor Kunal Nayyar.

Raj works in the physics department at the California Institute of Technology, or Caltech, where his research focuses on astrophysics and trans-Neptunian objects. The character is from New Delhi, India, and has a Ph.D.; he is one of the show's four central male characters alongside Leonard, Sheldon, and Howard.

Raj is often confused with Howard Wolowitz because they are close friends and coworkers, but Howard is an aerospace engineer rather than an astrophysicist. Raj is also distinct from Leonard and Sheldon, who are both physicists. A memorable part of Raj's early storyline is his selective mutism around women, which initially made it difficult for him to speak without alcohol or medication.

Kunal Nayyar played Raj throughout the show's original run, from its 2007 premiere through the series finale in 2019.