Jeffrey David Sinclair was a human Starfleet officer in the 23rd century. He eventually became a Federation ambassador.

Sinclair was born in Bradbury City, Mars on 3 May 2218. He attended Starfleet Academy from 2236 to 2240.

In 2258, Sinclair commanded Deep Space Station B-5, in the Euphrates Sector. The following year, he married his long-time girlfriend, freighter captain Catherine Sakai. In November, their son David Sinclair was born.

After a diplomatic assignment in 2281, Ambassador Sinclair disappeared near the galactic rim. (Star Trek: Pendragon)

This character can be considered the Star Trek-universe counterpart of Commander Jeffrey Sinclair from the sci-fi series Babylon 5. He is the great-grandfather of Timothy Sinclair.
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