Katz's Deli in the Lower East Side hosted a fake orgasm contest Friday afternoon in honor of the 30th anniversary of Meg Ryan's iconic scene in "When Harry Met Sally" ... ya know, when she's losing it during a meal with Billy Crystal.

The famous scene was filmed inside the deli known for its pastrami sandwiches ... so diners were challenged to recreate the big O in front of a lunchtime crowd. Prizes were on the line.

Ya gotta see our video ... women are going absolutely wild at tables inside the restaurant, giving their best bedroom performances and pulling out all the tricks in the book. No help needed.

Seriously, this is the type of thing you need to see and hear to believe. 

We're hoping you've never experienced a fake orgasm in real life -- and we're pretty sure you've never seen one in a deli -- but let's be real, you probably have ... and here's definite proof women know how to fake it.