Blue Ivy Carter Busts a Move at Cousin's Birthday Party!!!

Blue Ivy Carter has a knack for stealing the spotlight ... whether it's ballet dancing or dabbing ... and this video does not disappoint.

Blue was at Solange Knowles' son's 13th birthday party over the weekend ... and when Big Sean's "Bounce Back" started blaring from the speakers the 5-year-old had no choice but to get her dab on.

Check it out ... her move was dab-rinse-and-repeat. Gotta hand it to Bey and Jay's kid -- she's got range. Remember her killing it at her school's dance recital?