Lady Gaga to Fans: Who Wants a Slice!?

Lady Gaga's rollin' in dough -- in fact, she just threw down more than $1,000 to buy pizza for her fans.

TMZ has learned Gaga ordered 80 cheese pizzas for her minions waiting in line for an album signing outside a Los Angeles Best Buy.

Just a couple hours ago Gaga twittered: "Sending all my little monsters little pizzas for waiting all night for me at best buy. I hope you're hungry...eat up I love u!"

Gaga placed the order through a local Papa John's -- and they confirmed 40 pizzas were delivered at 3pm PST today, and 40 more will be delivered at 6. Altogether, the pop star's bill was over $1,000.

For the record, we're told Gaga tipped "very, very well."