Kapitänleutnant Wilhelm Otto Walther Schwieger (7 April 1885 – 5 September 1917) was a German military officer. He was a U-boat commander in the Imperial German Navy (Kaiserliche Marine) during First World War. In 1915, he sank the passenger liner RMS Lusitania with the loss of 1,199 lives.

In 1903, he joined the Imperial German Navy and from 1911 onwards he served with the U-boat Service. In 1912, he took over the command of the U-14. After the outbreak of World War I in 1914 he was promoted to Kapitänleutnant and given command of the U-20. As a submarine captain, Schwieger has been noted for his cavalier approach to attacking without being sure about the identity or nationality of his target, sometimes in breach of orders to the contrary. His policy has been described as 'shoot first and ask questions later'.

On 1 February 1915, he attacked the hospital ship HMHS Asturias, but the attack failed.

On 7 May 1915, Schwieger was responsible for the U-20 sinking passenger liner RMS Lusitania leading to the deaths of 1,199 people, an event that played a role in the United States' later entry into World War I. He also torpedoed RMS Hesperian on 4 September 1915 and SS Cymric on 8 May 1916. On 31 May 1917, his U-boat U-88 sank the Miyazaki Maru during that ship's voyage from Yokohama to London, causing the loss of eight lives.

Schwieger was killed in action on 5 September 1917. His U-boat U-88 most likely struck a mine. It sank north of Terschelling at 53°57′N 4°55′E / 53.950°N 4.917°E / 53.950; 4.917 with the loss of all 43 hands.

During his wartime career, Schwieger captained three different submarines, on a total of 34 missions. He sank 49 ships, measuring 183,883 gross register tons (GRT). Schwieger was represented in the docudrama "Lusitania: Terror At Sea" in 2007, where he was played by actor Florian Panzner.

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