SS Ajax was a Norwegian cargo ship that was destroyed with explosive charges by SM UC-17 in the English Channel 30 nautical miles (56 km) north of Ouessant, Finistère, France, while she was travelling from Rufisque, Senegal to Liverpool, United Kingdom.

She was completed in August 1904 under the name Spir but was renamed Bøilefos in 1912 and Ajax in 1915.

She had a triple expansion steam engine driving a single screw propeller.

[1] On 22 February 1917, Ajax was on a voyage from Rufisque, Senegal to Liverpool, United Kingdom.

She was stopped and destroyed by SM UC-17, 30 nautical miles (56 km) north of Ouessant, Finistère, France.