The late great Grumpy Cat still has one of her 9 lives left ... to fire off a lawsuit at Internet stores allegedly selling counterfeit merchandise.
The late feline's company -- Grumpy Cat Limited -- is suing to stop corporations and all other entities from producing and selling rip-off gear featuring GC's famous name and furry mug.
According to the legal docs ... the official site for Grumpy Cat t-shirts, hats, coffee mugs and more is grumpycats.com, so it wants the court to help shut down all other Internet shops hawking copycat items.
The company also wants the profits from all the alleged rip-off stores, claiming they're committing trademark infringement with every Grumpy tchotchke they sell.
As we reported ... Grumpy Cat -- government name Tardar Sauce -- died in May from complications from a urinary tract infection. The kitty was a marketing sensation, with countless products bearing her sour puss sold around the world. She also appeared in commercials and even got her own Lifetime Christmas movie.
The cat was 7 but clearly she still lives on ... in online retail, and now in court.