Ajax is a floating crane built to move and install the canal locks and other large parts of the Panama Canal. Ajax also helped in ship repairs and clearing the canal as needed. Ajax and her identical sister crane, the Hercules, were the largest floating cranes at time of completion, able to install the massive Panama Canal locks. Ajax could lift a maximum of 250 tons to a height of 21 feet (6.40 m), with a close reach. At Ajax's far reach she could lift a maximum of 100 tons. Ajax and Hercules were built by Deutsche Maschinenbau AG (1910-1977) . After the Ajax and Hercules, Deutsche Maschinenbau AG later made the Langer Heinrich, or Long Henry in 1915, in use for 100 years.

A crane vessel, crane ship, crane barge, or floating crane is a ship with a crane specialized in lifting heavy loads, typically exceeding 1,500 t for modern ships. The largest crane vessels are used for offshore construction.