Jay Adams Dead -- Legendary Skater Dies of Heart Attack

Jay Adams -- a legendary skater who was portrayed by Emile Hirsch in "Lords of Dogtown" -- has died of a heart attack ... TMZ has learned

Sources connected with the skater tell TMZ ... he died late Thursday of an apparent heart attack in Mexico.

We're told Adams was there with his wife and the 2 were on a long surfing holiday. They had been there for 3 months.

Family sources tell us ... the 53-year-old has been sober for months and had no history of heart problems.

This was the first time in 20 years Adams was allowed to leave the U.S. He had been in and out of jail since the '80s on various felony drug charges.