Lindsey Vonn & P.K. Subban

Welp, this is sad ...

Lindsey Vonn and P.K. Subban have sold the Beverly Hills mansion they bought together ... just 6 months after calling off their engagement.

The Olympic skiing legend and the NHL star purchased the 5,500 square foot pad for $6.75 mil back in 2020 ... and it seemed it would be their home base for years to come.

But the two called it quits in Dec. 2020 and quickly put the Italian-style villa on the market.

The place is sick ... especially the yard, a private sanctuary which features a slick pool, spa and fire pit.

Final sales price ... $6.9 million, according to the L.A. Times. It's unlikely they walked away with any sort of real profit after all of the expenses and…