Robert James-Collier (born 23 September 1976) is a British actor widely known for his roles as Liam Connor in Coronation Street, Thomas Barrow in Downton Abbey, and Martin Evershed in Ackley Bridge.

James-Collier was born on 23 September 1976 in Salford, Greater Manchester, to parents James and Anne Collier as Robert James Collier. When he became an actor, he hyphenated his middle name and surname to form a new surname, to comply with the rules of Equity and avoid confusion with another actor named Robert Collier.

James-Collier was educated at St Patrick's Roman Catholic High School in Eccles, Greater Manchester. He studied business at the University of Huddersfield for his bachelor's degree, and later obtained a master's degree in marketing at the University of Manchester Institute of Science and Technology.

With no acting experience, James-Collier auditioned for the series Down to Earth. Stars Ricky Tomlinson and Denise Welch were convinced by his talent, and he got the part of the womanising pub landlord. In 2006, he appeared in New Street Law and played a small part as 'Stud' in Shameless series 3, episode 5 under the name of Rob Collier.

In 2006, he joined Coronation Street as Liam Connor, joint owner of the Underworld factory. He left the show in October 2008. In an interview in early 2008, he announced he would leave the soap but planned to return. However, in June 2008, it was reported that the character of Liam was set to be 'brutally' killed off as part of a murder-mystery plotline where three well-known residents fell under suspicion for the crime. He soon modelled for British catalogue retailer Argos, appearing in the Autumn/Winter 2007 and Spring/Summer 2008 catalogues.

James-Collier achieved international recognition as the scheming, lonely gay footman (and later under-butler) Thomas Barrow in the historical drama series Downton Abbey (2010–2015), subsequently appearing in the franchise's three feature films, Downton Abbey (2019), Downton Abbey: A New Era (2022) and Downton Abbey: The Grand Finale (2025).

He played Kevin O'Dowd in ITV's 2016 crime drama The Level. In 2017, he starred in British horror film The Ritual; The Guardian described his performance as "a fierce screen presence". He had a principal role in the "Cold River" episode of Vera, aired in 2018.

In 2019, it was announced that he would be cast in the third series of Channel 4 school-drama Ackley Bridge as Martin Evershed.