Megamania gripped the Big Apple as dream-big New Yorkers yesterday traded hard-earned dollars for a chance to cash in on tonight’s $312 million Mega Millions jackpot.

From Crown Heights to Corona, ticket buyers took a shot at changing their lives for the price of gum.

Teresa Baxter, 49, bought just one ticket, in Astoria, Queens, figuring, “If it’s meant to be, it will happen.”

Retired trucker Thomas Planz, 76, got 45 tickets — and said if he wins, he’s off to Las Vegas to “find a nice 25-year-old woman and have some fun.”