Thomas Cullen (born 17 July 1985) is a Welsh actor and director. He had roles in the independent film Weekend (2011), as Anthony Foyle, Viscount Gillingham in the television series Downton Abbey, and as Sir Landry in the historical drama series Knightfall. He also appeared in another historical drama playing the role of Thomas Seymour in Becoming Elizabeth.

Early life
Cullen was born in Aberystwyth. He is the son of two writers. His father is Irish and his mother is English. He spent his early years in Llandrindod Wells and moved to Cardiff at age 12, where he attended Llanishen High School. He has two siblings.

Before pursuing an acting career he was involved in music. He graduated from the Royal Welsh College of Music and Drama in 2009 with First Class Honours degree in Acting after spending a year at the Central School of Speech and Drama.