The Bayern-class battleships were Germany's answer to the British Queen Elizabeth class, which had introduced 15-inch guns to the Royal Navy. Design work began in 1910 against the backdrop of the Anglo-German naval arms race, and the calibre of the main armament was the central question. Earlier German dreadnoughts carried 30.5-centimetre guns. Bayern's designers settled on 38-centimetre weapons, accepting the additional cost in exchange for a decisive jump in shell weight. She displaced over 32,000 tonnes at full load, was nearly 180 metres long, and could make 22 knots on trials. Her keel was laid in December 1913. She launched in February 1915. She was finally ready for service on 15 July 1916, a month and a half after the Battle of Jutland had passed her by.

Bayern's only significant combat operation came in October 1917, during Operation Albion, the German invasion of the Russian-held Baltic islands of Saaremaa and Muhu. She steamed into Tagga Bay alongside the battlecruiser Moltke and four König-class battleships to bombard Russian shore batteries. At 05:07 on 12 October, while moving into her firing position at Pamerort, she struck a naval mine. The explosion killed seven men, allowed a thousand tonnes of water into the hull, and dropped her forecastle by two metres. She fired on the battery at Cape Toffri despite the damage and was released from her station later that day. Temporary repairs failed; she had to be towed back to Kiel for two months of work in dry dock. That was her war.

On 21 November 1918, ten days after the Armistice, Bayern sailed from Wilhelmshaven with most of the High Seas Fleet under the command of Rear Admiral Ludwig von Reuter. They rendezvoused with a British light cruiser and then with a flotilla of 370 British, American, and French warships that escorted them to Scapa Flow. The Germans had not lost the war at sea, exactly. They had simply been outproduced and outwaited. The bulk of the fleet had not fought a battle since Jutland, and morale had collapsed into mutiny in October. The ships now riding north were manned by skeleton crews. The guns had been disabled by the removal of their breech blocks. The fleet was, in every meaningful sense, already finished.

The internment dragged on for seven months while the Allied powers argued over the terms of the Treaty of Versailles. Reuter, isolated at Scapa Flow with limited news, believed the British intended to seize his ships on 21 June 1919, the original deadline for German signature. The deadline had actually been extended to 23 June, but Reuter did not know that. On the morning of the 21st, the British Atlantic Fleet sailed out of Scapa Flow for training exercises. At 11:20 Reuter transmitted the prearranged order. Across the anchorage, German sailors opened sea valves, smashed sight glasses, and jammed open watertight doors. Bayern slid stern-first under the surface at 14:30 in the afternoon. The largest scuttling in naval history sent fifty-two ships, including ten battleships and five battlecruisers, to the bottom of Scapa Flow.

Bayern was salvaged in September 1934 and towed to Rosyth, where she was broken up for scrap the following year. The bulk of the great battleships rose from Scapa Flow in the 1920s and 1930s as Cox and Danks and later Metal Industries pioneered techniques for raising sunken capital ships. But not everything came up. Bayern's main battery gun turrets fell out of the inverted hull as she rose and remain on the seabed today, accessible to recreational divers in the cold green water of Scapa Flow. Her bell was eventually returned to Germany and now hangs in the Kiel Fördeklub. The ship that was supposed to lead a new battle squadron into Britain's North Sea backyard rests, in pieces, in the same waters her crew chose over surrender.