A classic Upper East Side co-op once owned by legendary dancer/actor Fred Astaire is currently on the market for $3.99 million. The seller is Montreal-born interior designer Garrow Kedigian, who has added bold high-gloss color to the “classic seven” unit at 863 Park Ave.

“I didn’t find out until my co-op board interview that [Astaire] lived here for about 10 years after World War II,” said Kedigian, in a 2013 House Beautiful Q&A about the renovation and restoration project he undertook.

“The owners before me, who purchased the place from him, had hardly changed a thing. It was a wreck. We scraped off 32 layers of paint and wallpaper.

The plaster had cracks you could stick a finger in. White shag carpeting covered the parquet! There was almost none of the original architectural detail you’d expect to find in a Beaux Arts Park Avenue building like this — only plain square beams.”

Kedigian purchased the L-shaped spread in “estate condition” in 2012 for $2.3 million and did an “elaborate” makeover, according to Compass, the brokerage firm that holds the listing.

The three-bedroom, three-bathroom apartment (which has seven main rooms total, hence the name) is 2,000 square feet and comes with the building’s only Juliet balcony. The building, which dates to 1906, is between East 77th and 78th streets.

There’s still a hint of Astaire there, hidden amid the stylish upgrade.

“On the dining room banquette, we reused the ancient velvet that still hung at these windows when I moved in,” Kedigian told House Beautiful. “It’s a conversation starter at parties to tell guests they’re sitting on Fred Astaire’s curtains.”

The listing broker is David Christopher Salvatore, of Compass.