Denis Lill (born 22 April 1942 in Hamilton, New Zealand) is a British actor.

Some of his many film and television roles include Fall of Eagles (1974), Edward the Seventh (1975), Survivors (1975), The Scarlet Pimpernel (1982), Rumpole of the Bailey (1983-1992), Mapp & Lucia (1985), Only Fools and Horses (1989-1992), Richard III (1995) and Evita (1996). He played Dennis in the 1990s sitcom Outside Edge. Lill twice appeared in the science fiction series Doctor Who: Dr Fendleman in the 1977 serial Image of the Fendahl and as Sir George Hutchinson in 1984's The Awakening. He also appeared as the drunken MP Sir Talbot Buxemley who died onscreen in an episode of Blackadder the Third.

He currently stars in ITV1 drama The Royal.

Lill is versatile in his use of national and regional accents and has played German, English, Welsh, and cockney characters in his various roles.