
Douglas Reith is a British actor and teacher. He is best known for his role as Lord Merton in the television series Downton Abbey (2010–2015), as well as its two follow-up films.
Reith was born in Melton, Suffolk. He studied acting at the Webber Douglas Academy of Dramatic Art. He began acting in the late 1970s, beginning with an appearance in International Velvet (1978) alongside Tatum O'Neal and Christopher Plummer.
He worked as an announcer and presenter at BBC Radio 3 for five years before leaving to study Greats at Christ Church, Oxford for four years beginning in 1989. He worked as a teacher, including at Westminster School, before resuming his acting career.
Reith joined the cast of Downton Abbey as Lord Merton in 2012, and alongside the cast was nominated for the Screen Actors Guild Award for Outstanding Performance by an Ensemble in a Drama Series at the 23rd Screen Actors Guild Awards. He reprised the role in the films Downton Abbey (2019) and Downton Abbey: A New Era (2022). In 2017, Reith was cast in Tim Burton's live-action remake Dumbo (2019). In 2019, he was cast in SAS: Red Notice (2021).

Rush
2013 · as Awards Presenter

SAS: Red Notice
2021 · as Sir Charles Whiteside

Dumbo
2019 · as Sotheby

Downton Abbey
2019 · as Lord Merton

Downton Abbey: A New Era
2022 · as Lord Merton

Downton Abbey: The Grand Finale
2025 · as Lord Merton

The Queen
2006 · as Lord Airlie

W.E.
2011 · as Lord Brownlow

The War Below
2021 · as Field Marshal Haig

Serial Teachers 2
2015 · as Le chef de la sécurité

Enid
2009 · as BBC Interviewer

International Velvet
1978 · as Howard

An Englishman Abroad
1983 · as Toby

The Happy Autumn Fields
1980 · as Fitzgeorge

The Queen's Sister
2005 · as Horace Featherstonehaugh

Amy
1984 · as Jimmy Martin

Bloodlines: Legacy of a Lord
1998