Sofia Vergara -- Heroic Maneuvers in Vegas During Casino Emergency

Sofia Vergara began 2012 by rushing to the aid of a young woman who collapsed on the floor of a Las Vegas casino ... TMZ has learned.

The "Modern Family" star was leaving Hyde nightclub at the Bellagio around 3 AM on New Year's Day ... when Sofia saw a woman hit the deck.

Sources at the scene tell us ... Sofia and a girlfriend rushed over to the woman to help. We're told Sofia's friend had medical training and was seen checking the woman's pulse.

Both Sofia and her friend tried to keep the woman calm ... and waited by her side until security personnel and paramedics arrived to the scene. We're told the woman was eventually transported to a nearby hospital.