Joshua Thomas Radnor (born July 29, 1974) is an American actor, filmmaker, author, and musician. He is best known for portraying Ted Mosby on the Emmy Award–winning CBS sitcom How I Met Your Mother (2005–2014). He made his writing and directorial debut with the 2010 comedy-drama film Happythankyoumoreplease, for which he won the Sundance Film Festival Audience Award and was nominated for the Grand Jury Prize.

In 2012, he wrote, directed and starred in his second film, Liberal Arts, which premiered at the 2012 Sundance Film Festival. In 2014, Radnor portrayed Isaac in the Broadway play Disgraced, which was nominated for the Tony Award for Best Play. He then starred as Dr. Jedediah Foster on the PBS American Civil War drama series Mercy Street, Lou Mazzuchelli in the musical series Rise, and as Lonny Flash in Hunters. In 2024, he returned to the theatre, appearing in the Itamar Moses play The Ally at The Public Theatre.