Captain Jonas Grumby was a Starfleet officer in the 24th century.
In 2364, he was the commander of the USS Minnow. Sometime in that year, he received an order about STFL Cargo Manifest 045-349374 from Commander Horton of Terrestrial Defense Division. His name, rank, and current assignment was from the order's heading. (TNG: "Conspiracy", okudagram)
This character was only mentioned in writing.
He was named after Jonas Grumby, a character from the television comedy series Gilligan's Island who operated a small vessel called the SS Minnow.