The Battle of Tirad Pass was a battle in the Philippine-American War fought on December 2, 1899 in northern Luzon in the Philippines, when a 60-man Filipino rearguard commanded by Brigadier General Gregorio del Pilar eventually succumbed to 300 Americans of the 33rd Infantry regiment under Major P.C. March.

The 24-year-old "boy general" del Pilar had noted the advantageous terrain of Tirad Pass (Pasong Tirad), and offered to defend it while Emilio Aguinaldo, President of the Philippine Republic, made good his escape through the mountains. The hand-picked force of Filipinos constructed several sets of trenches and stone barricades, all of which dominated the narrow trail that zigzagged up towards the pass.

At about 0630 on the morning of December 2, the American advance up this very trail was swiftly halted, leading to several U.S. casualties. The Americans abandoned the idea of a frontal assault, instead sending elements of their force to outflank the determined defenders. Texan sharpshooters stationed themselves on a hill overlooking the trenches, and proceeded to whittle down the Philippine rearguard with measured volleys. With the help of local villager Januario Galut, another group of Americans was led up a trail by which they could emerge to the rear of the Filipinos.

Finally, over five hours after the battle had started, Americans fell upon the flank and rear of the outnumbered defenders, killing some 52 of the 60 Filipinos. Among the dead was the inspirational General del Pilar, shot through the neck at the height or end of the struggle (depending which eye-witness accounts are to be believed). The Americans lost 2 dead and 9 wounded.

A diary belonging to del Pilar was later recovered by the Americans. Its poignant final entry, written on the night of 1 December, read:

"The General has given me the pick of all the men that can be spared and ordered me to defend the Pass. I realize what a terrible task has been given me. And yet I feel that this is the most glorious moment of my life. What I do is done for my beloved country. No sacrifice can be too great."

In honor of Gen. Del Pilar's heroism, the Philippine Military Academy was named Fort Del Pilar and a historical marker placed at the site of the battle.