Jun'yō Maru (順陽丸) was a cargo steamship that was built in Scotland in 1913, served a succession of British owners until 1927, and was then in Japanese ownership until a Royal Navy submarine sank her in 1944.

In 1944 Jun'yō Maru was being used as a hell ship, carrying about 4,200 Javanese slave labourers and about 2,300 Allied prisoners of war (PoWs) when the submarine HMS Tradewind sank her.

Robert Duncan & Co built the ship at Port Glasgow as yard number 324, launching her on 30 October 1913.

She had a single screw, driven by a three-cylinder triple-expansion steam engine built by John G. Kincaid & Company of Greenock that was rated at 475 NHP.

[2] The ship's first managers were Lang & Fulton Ltd, a Scottish firm who operated a small number of tramp steamships, to each of which they gave a name beginning with "Ard–".

[7] In 1921 the Anglo-Oriental Navigation Company bought Hartmore, renamed her Sureway,[9] and made Yule, Catto & Co her managers.

[10] In 1927 Sanyo ShaGoshi Kaisha bought the ship, renamed her Junyo Maru, and registered her in Takasago.

By September 1944 Jun'yō Maru had been fitted out as a prison ship with bamboo scaffolding between her decks and bunks three or four deep in her holds.

She embarked about 4,200 or 4,300 Javanese forced labourers (rōmushas) and an estimated 2,200–2,300 Allied PoWs at the port of Tanjung Priok on Java near Batavia, to take them to Pekanbaru to build a railway across Sumatra.

On 17 September was heading for Padang, escorted by a small Imperial Japanese Navy ship that survivors described as a corvette or gunboat.

A compiled list of names puts the number of allied POW deaths at around 1,449 but it is unknown exactly how many rōmushas perished in the disaster.