Greg Tiernan (born on June 19, 1965 in Dublin, Ireland) is an Irish-born Canadian animator, director and voice actor. He is the Chief Creative Officer, co-founder and co-owner of Nitrogen Studios. He was the director of Thomas and Friends from 2009 to 2012. In the twelfth season, he worked as unit director for Nitrogen Studios. He began work directing the series after the CGI transition, taking over from Stephen Asquith.
He was born in Ireland and started Nitrogen Studios in 2003 with Nicole Stinn.
- "Sausage Party" (2016)
- "City in Crisis" (2015)
- He is married to Nicole Stinn.
- He has been working in the animation industry for twenty-seven years.
- Tiernan is a fan of the Railway Series. So much in fact, that he owns a copy of both The Island of Sodor: Its People, History and Railways and Sodor: Reading Between the Lines.
- According to an interview with SiF, Greg Tiernan says he would like to remake Pop Goes the Diesel and Dirty Work. And, if it was his choice, he would reintroduce every character ever introduced.
- Tiernan was involved in the animation of "Happily N'Ever After", the last film in which George Carlin played a part.