Captain Richard Arnold was a Human Starfleet officer in the 24th century.
In 2354, he was named as a Starfleet Operational Support Services officer on a directory placard in Starbase 32, Maxia sector. His room number was 34429. (TNG: "Violations", directory)
In 2368, he was named as a Warp Technologies Development Group officer on the second version of the dedication plaque of the USS Enterprise-D. (TNG: "Silicon Avatar", dedication plaque)
Arnold's name was an inside reference to production staff associate Richard Arnold.