Ieu Koeus (Khmer: អៀវ កើស; 1905 – 14 January 1950) was a Cambodian politician.

Considered an intellectual, he was instrumental in the formation of the Cambodian Democratic Party in April 1946, created a self-declared government on September 20, 1949, was replaced by Yem Sambaur on September 29.

On 14 January 1950, a hand grenade was thrown into the party headquarters, fatally wounding Koeus, who led the National Union Movement.

[2] The man throwing the grenade was captured and arrested, admitting, then later denying, that he was a member of the opposing Liberal party.

Blame for the assassination, however, varies from the French, King Sihanouk, Yem Sambaur, and rebel Issaraks with little evidence available.