Sir Frank Watson Dyson, KBE, FRS,[1] FRSE (8 January 1868 – 25 May 1939) was an English astronomer and the ninth Astronomer Royal who is remembered today largely for introducing time signals ("pips") from Greenwich, England, and for the role he played in proving Einstein's theory of general relativity.

He is credited with organising expeditions to observe the 1919 solar eclipse at Brazil and Príncipe, which he somewhat optimistically began preparing for prior to the Armistice of 11 November 1918.

The observations confirmed Albert Einstein's theory of the effect of gravity on light which until that time had been received with some scepticism by the scientific community.

[11] Dyson died on board a ship while travelling from Australia to England in 1939, and was buried at sea.

Actor Alec McCowen was cast as Sir Frank Dyson in the TV series Longitude, broadcast in 2000.