I-124 was a submarine of the Imperial Japanese Navy sunk outside Darwin, Australia on 20 January 1942 during the Second World War. I-124 was conducting mine laying operations and attacking shipping along with three other submarines outside of Darwin Harbour, Australia.
I-124 attacked the corvette HMAS Deloraine on 20 January. Its commander, Lieutenant Commander Desmond Menlove, was alerted to the approaching torpedo, and utilising skillful teamwork and leadership, the Deloraine fought the I-124 until the submarine half-rose to the surface, where it was depth-charged at point-blank range. I-124 was sunk with the loss of 80 lives. Other vessels, including HMAS Lithgow, HMAS Katoomba, and USS Edsall, arrived after the sinking, and also laid attack patterns in the area.
The submarine has been surrounded in controversy since then, with unsubstantiated claims it was connected with the sinking of HMAS Sydney II the previous November; that its crew remained alive for some time and divers heard crew movement inside the hull, and that codebooks were recovered from the wreck. Several attempts have been made to raise and/or enter the vessel. There have also been disproved claims of mercury inside the hull, and of other submarines sunk nearby.
The I-124 remains intact outside Darwin today. Her resting site is protected under Australia's Historic Shipwrecks Act.