James Dolan is shutting down all talk of selling the New York Knicks ... laughing at the notion and straight-up saying it's not happening.
The rumors started to swirl earlier this week ... when investment analyst Jonathan Boyar predicted Dolan would put the team up for sale after the new MSG Sphere opens up in Las Vegas next year.
An MSG rep was quick to deny the speculation ... saying there were "no plans" to sell both the Knicks and New York Rangers.
Dolan doubled down on the statement as he was leaving businessman Noah Tepperberg's birthday party at LAVO in West Hollywood .