Ashley Olsen, 21, and Jared Leto, 36 -- who dated briefly in 2005 -- turned heads while holding hands at the Art of Elysium gala in L.A. on Jan. 12, Us Weekly reports in its latest issue, on newsstands now.
"They looked like a couple and they were making out," a witness tells Us.
But an Olsen insider denies the duo are back on: "They aren't back together. They're friends."