Jennifer Lopez Just a Reminder ... My Butt Is Out of Sight!

6/5/2014 8:00 AM PDT

Jennifer Lopez's Butt -- Just a Reminder: My Backside's Outta Sight!

Jennifer Lopez did her first ever concert in her hometown of the Bronx last night, and she did not hold back the goods ... giving the crowd a view of her prized backside.

J.Lo's free show at Orchard Beach -- in advance of her new album coming out later this month -- featured actual singing and multiple costume changes ... most of which showed off her rear end, thankfully. 

The butt show was clearly a response to the latest challenger to the ass throne ... Bradley Cooper

One word, Cooper -- fishnets ...