Built at Elswick[1] and nearly identical to her sister ship, Harald Haarfagre was named after Harald I of Norway, known as "Harald Fairhair" in English, the semi-mythical first king of a united Norway. Built as a typical pre-dreadnought battleship on a smaller scale, she carried guns of a wide range of calibers: two 8.2-inch guns in barbettes, six 4.7-inch, six 3-inch, and six smaller quick-firing guns. The ship could manage a speed of over seventeen knots. Protected by belt armor of seven inches thickness, the ship also featured gun barbettes with nearly eight inches of steel armor and an armored deck.
A vital part of the Royal Norwegian Navy, Harald Haarfagre performed ordinary duties until she was considered "unfit for war" in the mid-1930s and disarmed. After the German invasion of Norway, she was seized by the Germans and rebuilt as a floating flak battery under the name Thetis. After the war Harald Haarfagre was used briefly as a floating barracks, and for transporting German POWs, before she was sold for scrapping in 1948.
It was intended to augment the Norwegian Panserskip fleet with the two ships of the, ordered in 1912, but after these were compulsorily purchased by the Royal Navy at the outbreak of the First World War, the Tordenskjold class and the slightly newer, two ship, remained in service the Norwegian navy long after they were obsolete due to a lack of suitable replacements.
Today the name KNM Harald Haarfagre is used on the Royal Norwegian Navy and Royal Norwegian Air Force Basic Training Establishment, located in Madla, Stavanger.