The ubi sunt motif in Old English literature refers to a common theme that reflects on the transience of life and the inevitability of death. The phrase "ubi sunt" is Latin for "where are they" and is often used in Old English poetry to lament the passing of time and the mortality of human beings. This motif is often found in elegiac poems and reflects on the impermanence of life and the fleeting nature of human existence. It serves as a reminder of the inevitability of death and the importance of living a meaningful life.