Gilbert de Clare, 5th Earl of Hertford and 1st Earl of Gloucester) (1180 - October 25 1230) was an English nobleman of the Norman period.

He was the son of Richard de Clare, 4th Earl of Hertford and Amice Fitzrobert . Both Gilbert and his father both were Magna Carta sureties.

In June 1202, he was entrusted with the lands of Harfleur and Montrevillers .

He was one of the Barons still opposing the arbitrary proceedings of the crown, who championed Louis le Dauphin , fighting at Lincoln under the baronial banner, and was taken prisoner by William Marshal, whose daughter he later married. He led an army against the Welsh in 1228 and captured Morgan Gam , who was released the next year. He joined in an expedition to Brittany, but died on his way back to Penros in that duchy. His body was conveyed home by way of Plymouth and Cranbourgh to Tewkesbury.

He was buried there, before the high altar of Tewkesbury Abbey, on November 10, a monument being erected by his widow, Isabel Marshall , sister of William Marshall, the Surety, and daughter of William Marshall, the Protector. Sir Gilbert de Clare and Isabel Marshall had a son, Sir Richard de Clare, Earl of Gloucester