What was the Tom Selleck sitcom from late or early

The Tom Selleck sitcom you're likely thinking of is "Magnum, P.I."

While it's not technically a sitcom, it was a popular detective drama series that ran from 1980 to 1988 and featured Tom Selleck in the lead role as the iconic private investigator Thomas Magnum.

If you're thinking of a later sitcom, you might be thinking of "Friends," where Selleck guest-starred as Richard Burke, Monica Geller's love interest, for several seasons.