Commander Ralph Frederick Seymour, CMG, DSO (6 January 1886 – 4 October 1922) was a British Royal Navy officer in the First World War.
He entered the Royal Navy, and was on 1 October 1902 posted as a midshipman to HMS St George, serving in the Home Fleet.
Throughout the First World War he served as Flag Lieutenant to Admiral Sir David Beatty, despite the fact that he did not possess a full training in signalling.
A badly-worded signal he sent during the German battlecruiser raid on Scarborough, Hartlepool and Whitby on 16 December 1914 caused Beatty's scouting forces to break off contact with the enemy, thus prematurely ending the pursuit.
After this, however, when Beatty's actions at Jutland began to receive hostile scrutiny, his attitude to Seymour changed and became much more negative.