Baron Merthyr is a peerage title in the Peerage of the United Kingdom. It was created in 1911, but was disclaimed for life by the fourth Baron in 1977.
Barons Merthyr (1911)
- William Thomas Lewis, 1st Baron Merthyr (1837-1914)
- Herbert Clark Lewis, 2nd Baron Merthyr (1866-1932)
- William Brereton Couchman Lewis, 3rd Baron Merthyr (1901-1977)
- Trevor Oswin Lewis, 4th Baron Merthyr (b. 1935)