Shane O'Neill, 3rd Baron O'Neill

Shane Edward Robert O'Neill, 3rd Baron O'Neill (1907–1944) was an Anglo-Irish peer and British Army officer. He served during World War II and was killed in action in Italy.

O'Neill was born on 6 February 1907 to The Hon Arthur O'Neill and his wife Lady Annabel Hungerford Crewe-Milnes. His mother was the eldest daughter of Robert Crewe-Milnes, 1st Marquess of Crewe. He was educated at Eton College, an all-boys public school in Eton, Berkshire, England. He did not attend university.

His brother Terence was a politician who became Prime Minister of Northern Ireland.

He married Anne Charteris, granddaughter of the 11th Lord Wemyss, in 1932. After his death she remarried, firstly to the 2nd Lord Rothermere, a press tycoon and former Tory MP, and later to Ian Fleming, the creator of James Bond, as well as having affairs with the Labour politicians Hugh Gaitskell and Roy Jenkins.

In 1929, O'Neill joined the Gillett Brothers Discount Company as a director.

On 30 August 1929, he was promoted to lieutenant in the 8th King's Royal Irish Hussars.