What battle in 1862 was the first battle between ironclad warships?

The Battle of Hampton Roads in 1862 was the first battle between ironclad warships.

The engagement took place on March 8 and 9, 1862, in Hampton Roads, Virginia. On the first day, the Confederate ironclad CSS Virginia attacked Union wooden warships, destroying USS Cumberland and USS Congress and damaging other vessels while attempting to break the Union blockade.

The next day, USS Monitor arrived and confronted Virginia. The two armored ships fought for about three hours, firing heavy guns at one another and attempting to maneuver and ram. Their duel ended without a decisive winner, but neither vessel could seriously penetrate the other's armor.

The battle is sometimes called the Battle of the Monitor and Merrimack, although Merrimack was the original name of the Union steam frigate whose burned hull was rebuilt as Virginia. Another common mix-up concerns the phrase “first ironclad battle”: CSS Manassas had entered combat earlier, at the Battle of the Head of Passes in October 1861. Hampton Roads is specifically recognized as the first combat between two ironclad warships.