The siege of Metz was a battle fought during the Franco-Prussian War from August 19 to October 27, 1870 and ended in a decisive Allied German victory.

The French Army of the Rhine under Franois Bazaine retreated into the Metz fortress after its defeat by the Germans at the Battle of Gravelotte on 18 August 1870. The fortress was promptly surrounded by German forces under Prince Friedrich Karl of Prussia. The French Army of Chlons was sent to relieve the Army of the Rhine but was itself encircled and annihilated by the German armies at the Battle of Sedan on 12 September.

Unable to capture the fortress by bombardment or storm, the besieging Germans resorted to starving the French to submission. French attempts to break out ended in defeat at the battles of Noisseville on 31 August 1 September and Bellevue on 7 October. French food supplies ran out on 20 October and Franois Achille Bazaine surrendered the fortress and the entire Army of the Rhine, some 193,000 men, into German hands on 27 October.

The annihilation of the French Army of the Rhine freed Prince Friedrich Karl's armies for operations against French forces in the Loire river valley for the rest of the war. Metz was annexed into the German Empire after the signing of the Treaty of Frankfurt on 10 May 1871.

François Achille Bazaine (13 February 1811 – 23 September 1888) was an officer of the French army. Rising from the ranks, during four decades of distinguished service (including 35 years on campaign) under Louis-Philippe and then Napoleon III, he held every rank in the army from Fusilier to Marshal of France. From 1863 he was a Marshal of France, and it was in this role that he surrendered the last organized French army to Prussia during the Franco-Prussian war, during the siege of Metz.

Sentenced to death by the government of the Third Republic following the war, his sentence was commuted to 20 years imprisonment in exile, from which he subsequently escaped. He eventually settled in Spain where aged 77, he died alone and impoverished in 1888.