Fat Joe Taps Busta Rhymes, French Montana, Rick Ross for 'Power to the Patients' Concert

Fat Joe's power circle is coming to aid his fight against shady hospital bills -- Busta Rhymes, French Montana, and Rick Ross are all set to perform with the Don this week ... TMZ Hip Hop has learned.

The function's going down Thursday in Washington, D.C., and will be hosted by Power to the Patients ... the org Joe's been supporting loudly in an effort to force transparency in hospital billing.

He and Power to the Patients have been demanding new legislation to back their cause, and, to that end, we're told Joe's scheduled a meet-up with lawmakers on Capitol Hill ... and a news conference with members of Congress.

The legendary rapper's not messing around ... bringing in A-list pals in rap for support. Thursday's concert will be part of a busy week of events in the nation's capital as the White House Correspondents Dinner goes down Saturday night.