The Islanders got another piece of business done before the opening of free agency on Tuesday.

Pending restricted free agent defenseman Alexander Romanov inked an eight-year extension worth $6.25 million annually, an industry source confirmed to The Post.

The deal will see the 25-year-old Romanov play out the prime of his career on Long Island, where he’s spent the last three seasons after coming over in a 2022 trade with the Canadiens.

After the Isles traded Noah Dobson over the weekend, Romanov was set to be their highest-paid RFA, and thus the most important piece of business for Mathieu Darche to get done ahead of Tuesday.

Simon Holmstrom, Max Tsyplakov, Emil Heineman and Marc Gatcomb are the club’s remaining RFAs.

Romanov had four goals and 16 assists in 64 games this season, averaging 22:18 of ice time.