Frongoch internment camp at Frongoch in Merionethshire, Wales was a makeshift place of imprisonment during the First World War and the 1916 Easter Rising.

Originally the camp housed German prisoners of war in a yellow distillery and crude huts, but in the wake of the 1916 Easter Rising in Dublin, Ireland, the German prisoners were moved and it was used as an internment camp for approximately 1,800 Irish republicans, among them such notables as Michael Collins, who were accorded the status of prisoners of war. Among the prisoners were the future Hollywood actor Arthur Shields and sportsman and referee Tom Burke. It is a common misconception that Éamon de Valera was also imprisoned at Frongoch; he was actually held at several prisons in England at this time.

Colonel Frederick Arthur Heygate Lambert was the camp commandant.

The Irish Republican internees elected their own commandants (this practice was followed in future imprisonments/internments) and established a chain of command. The camp became a breeding ground for the guerillas of the Irish rebels, with inspired organisers such as Michael Collins giving impromptu lessons in guerrilla tactics. Later the camp became known as ollscoil na réabhlóide, the "University of Revolution".

The prisoners were allowed to cross the Afon Tryweryn to a meadow on Rhyd y Defaid (lit. 'sheep-run') Farm where they played various sports, including Gaelic football.

Lord Decies was appointed as Chief Press Censor for Ireland after the Rising in 1916, and he warned the press to be careful about what they published. William O'Brien's Cork Free Press was one of the first papers he suppressed under the Defence of the Realm Act 1914 (DORA regulations) after its republican editor, Frank Gallagher, accused the British authorities of lying about the conditions and treatment of republican prisoners at the camp.

In October, the camp was overrun by rats.

The camp was emptied in late December 1916 when David Lloyd George replaced H. H. Asquith as Prime Minister.