Dudley Moore has died at his home in New Jersey.
The entertainer was 66 and had been suffering from degenerative brain disease for the last few years.
Moore achieved worldwide stardom for his 1960s partnership with the late Peter Cook.
He also became an unlikely Hollywood heart-throb after his starring roles in the movies 10 and Arthur.
Moore died at 11 a.m. (4 p.m. Irish time), said publicist Michelle Bega in Los Angeles.
Ms Bega said Moore died surrounded by his family and friends.
He died of pneumonia as a complication of progressive supranuclear palsy, she added.
The condition robbed him of his speech and rendered him virtually immobile.
The 5ft 2in performer made his illness public in September 1999, revealing his vision had become hazy, his walking was impaired and speech slurred.
He accepted his CBE from Prince Charles last November while confined to a wheelchair.
PA