Jaimie Alexander (born March 12, 1984) is an American actress who is best known for her television role as Jessi on the ABC Family science fiction teen drama series Kyle XY from 2006 to 2009.

She played Sif in the Marvel film Thor, its 2013 sequel Thor: The Dark World, and the Agents of S.H.I.E.L.D. episodes "Yes Men" and "Who You Really Are.", and will reprise her role in the 2017 sequel Thor: Ragnarok. She also played Nikki Atkins in the ABC Studios TV show Perception.