Met Gala Fashion Trains ... The Growing Trainsetters?!

All aboard the Met Gala fashion train!!!

Elaborate -- and super long -- dress trains have been a staple at the Met Gala for years ... with Rihanna among the ultimate trendtrainsetters.

RiRi rolled out a yellow train behind her 2015 Met Gala dress ... check it out -- it flowed down several stairsteps as she climbed her way up to the annual NYC event.

Lady Gaga ran a train at the 2019 Met Gala ... in a pink dress, no less.

The singer even had some guys lend a hand with her train ... they had the fabric in one hand and umbrellas in the other.

Amelia Gray kept the trend alive last year ... with her own little twist.

Instead of trailing off the back of her dress, Amelia's train was coming off her headdress.