What is Rashguard in BJJ?

A rashguard is a tight-fitting synthetic athletic shirt worn during no-gi BJJ training. Originally from surfing, it protects against mat burn, reduces skin-to-skin contact (lowering infection risk), and wicks away sweat. In competition, rashguards are often required to be ranked (color indicating belt level) and may need to be IBJJF approved. Under the gi, some practitioners wear rashguards for hygiene and comfort.