Lieutenant-Colonel Sir Eric Richard Thesiger DSO, TD (17 February 1874 – 2 October 1961), styled The Honourable from 1878, was a British soldier and page to Queen Victoria.
He was the fourth son of Frederic Thesiger, 2nd Baron Chelmsford and his wife Adria Fanny Heath, daughter of Major-General John Coussamker Heath. His older brothers were Frederic Thesiger, 1st Viscount Chelmsford and the diplomat Wilfred Gilbert Thesiger. Thesiger was educated at Winchester College and in 1884, he was nominated Page of Honour to the Queen, a post he fulfilled for the following six years. In 1893, he became a Staff Commissioner of Police.
Thesiger joined the Imperial Yeomanry as a private during the Second Boer War, when he was appointed a lieutenant of the 15th Battalion (Imperial Yeomanry) on 29 November 1900. On 1 November 1901 he was promoted to captain in the battalion, with the temporary rank of captain in the Army. He stayed in South Africa until the war ended in May 1902, and left Port Elizabeth for Southampton on the SS Colombian two months later. In late 1902 he became a second lieutenant of the Surrey Yeomanry. He was transferred as major from the Yeomanry into the Territorial Force in 1908. In the First World War Thesiger was wounded twice and was mentioned in despatches as many times.