EXCLUSIVE

Lindsay Lohan's ego might be her downfall -- because TMZ has learned, she just shut down a lucrative offer to do "Dancing with the Stars" ... because she doesn't want to do reality TV.

Sources close to Lindsay tell us, the actress was made several offers to join the DWTS cast this upcoming season -- offers that maxed out at $550,000.

But Lindsay -- who still owes hundreds of thousands in back taxes -- shut them down, telling friends she'd never consider doing reality TV ... she wants to stick to films.

But there's one problem -- after "The Canyons" fiasco, she's basically made herself unhireable. And as the saying goes, beggars can't be choosers.