The 4th California Infantry was a volunteer infantry regiment recruited from northern California during the American Civil War.

It was organized at Sacramento, Placerville, and Auburn in September and October 1861.

Most of the recruits, caught up in war fever, expected to be sent to the eastern battlefields.

They were disappointed to be instead ordered to garrison duty and related tasks on the West Coast, where they spent the remainder of their enlistments.

The regiment served principally in the District of Oregon, (Oregon and Washington Territory), and in the District of Southern California, although some companies were shifted to Arizona later in the war.