EXCLUSIVE

Katherine Heigl claims a major drug store chain is shamelessly using her image to hawk hemorrhoid cream, Rid and all things drug store.

Katherine filed a lawsuit -- obtained by TMZ -- in which she claims she was coming out of Duane Reade in NYC last month, when a paparazzo snapped a pic of her carrying a Duane Reade bag.

Katherine says she was horrified to learn the drug store later tweeted, "Love a quick #DuaneReade run? Even @KatieHeigl can't resist shopping #NYC's favorite drugstore."

So now Katherine is gunning for the drug store chain in court, demanding $6 Mil.

And here's the best part. Katherine turns the lawsuit into a resume, saying, "Plaintiff is a highly successful television and motion picture actress, producer and celebrity." It goes on to list her various credits, adding, "Plaintiff continues to be in high demand in the entertainment industry."

And braggie Katie adds, "A recent search for 'Katherine Heigl' on the Google search engine returned over 3.2 million results." And she says she boasts 754,000 Twitter followers.

Katherine also says she'll donate her monetary judgment to the Jason Debus Heigl Foundation which focuses on animal welfare.