This competition is pure garbage!

A new “Trash Train” photo competition is encouraging straphangers to snap away at their gross commutes — with a $500 prize for whoever finds the city’s filthiest subway car.

The stomach-churning contest, hosted by the Transport Workers Union Local 100, underscores a serious issue, too. The union claims the increase in dirty cars is the result of cleaning crews getting axed by the MTA.

“It’s disgusting!” the union says on the competition site, calling the trashy rides “the MTA’s dirty secret.”

“You know it, the transit union knows it, but the MTA does not seem to get it!” the union says. “Trash-filled subway cars are coming back because the MTA has cut cleaner jobs. If you encounter a filthy subway car, it’s because the MTA doesn’t have the staff to clean it — because they decided to spend their budget $$ on something else — like million-dollar consultants.”

The grand prize will be handed out at the end of next month, with commuters able to enter on the official website or through Instagram using the hashtag #trashtrain.

Even MTA employees are encouraged to enter, though the rules advise them to make sure they’re off duty because “MTA discipline has no bounds.”

“By entering our photo contest for the filthiest subway car, you are helping make our case that cleaner jobs should be restored,” the union says on the site. “We run a world-class operation — and New York’s transit system is second to none. The MTA shouldn’t skimp on hiring the staff they need to deliver clean cars to our 6.5 million daily riders.”

The rules state that photos cannot have MTA employees, passengers’ faces or homeless people in them — and anything that is obviously staged will be ruled out.

There is bound to be stiff competition — video of a southbound 2 train brimming with trash went viral in May, while MTA data shows complaints of “soiled” subway cars are higher this year than in all of 2017.