Fort Williams was a timber and earthwork fortification constructed in Alexandria, Virginia as part of the defenses of Washington, D.C. during the American Civil War.

Built by the 2nd Connecticut Heavy Artillery Regiment, Fort Williams had a perimeter of 250 yards, and space for 13 guns.

[1] The Fort is now located in the backyard of a property in the Seminary Ridge neighborhood.

[2] Portions are also included in a 7.80 acres (31,600 m2) Alexandria, Virginia city park, at 501 Fort Williams Parkway.

[3] A small cemetery with the gravesites of several Union soldiers was located in the woods off the southeast corner of Seminary Road and Fort Williams Parkway.