31st Field Artillery Regiment, is a unit of 31st Infantry Division of the Philippine Army under the USAFFE, mobilized in August 1941 but was equipped in November, and was in action December 1941 to April 9, 1942.

It trained in Camp Del Pilar in Dau, Pampanga the Field Artillery School of Philippine Army.

Lieutenant Colonel Harry J. Harper was selected as senior instructor of the regiment but eventually commanded it as war progressed.

[2] The division was in Central Plains and covering Zambales west coast when Japanese started its invasion in the Philippines.

The regiment saw combat during the series of delaying actions of North Luzon Force under Major General Jonathan Wainwright.