The Black Keys -- We're Donating a Shirtload of Money ... To Our Little League

The Black Keys are about to make a HUGE donation to their hometown little league ... 'cause the custom jersey for the team they sponsor is now on sale to the public -- with every penny heading to the league.

The shirt went up for sale on the band's website Monday in an effort to raise funding for the West Akron Baseball League in Ohio.

As you may recall ... the Keys sponsored a team in the league last season ... and gave them bad ass jerseys with the band's name on it. They even signed 'em after the season was over as a souvenir.

The band says the money will go towards a variety of projects -- like lowering registration fees, buying uniforms, replacing benches/backstops and upgrading equipment.