The First Wirth cabinet (German: Erstes Kabinett Wirth) was the fifth democratically elected Reichsregierung of the German Reich. It was named after Reichskanzler (chancellor) Joseph Wirth and took office on 10 May 1921 when it replaced the Fehrenbach cabinet.
The cabinet was once again based on the "Weimar Coalition" of Social Democratic Party of Germany (SPD), the Catholic Zentrum and the German Democratic Party (DDP). Fehrenbach's cabinet had been based on the Zentrum, DDP and the German People's Party (DVP).
The First Wirth cabinet resigned on 22 October 1921 in protest over the handling of the Upper Silesia plebiscite by the League of Nations. It was replaced on 26 October by another cabinet led by Wirth.
Wirth had been Finance Minister under chancellor Fehrenbach, whose cabinet had resigned on the evening of 4 May 1921 over its inability to agree on a new proposal to present to the Allies on the question of war reparations. On 5 May, the Allies then issued what became known as the "London Ultimatum". It demanded that by 11 May the German government accept the war reparations schedule and its total sum, punctually comply with disarmament according to the Treaty of Versailles and initiate trials of German war criminals. In the case of non-compliance, the Allies would occupy the whole Ruhr, Germany's industrial heartland. This would be in addition to measures already announced: occupation of Düsseldorf, Duisburg and Ruhrort as well as financial sanctions in the form of a levy on German exports.
It took the German parties until 10 May to decide on their positions towards this ultimatum. The independent social democrats (USPD), SPD and Zentrum favoured acceptance. The DDP was split and left the decision to its Reichstag delegates. Attempts by the SPD to win the USPD for a coalition failed because the latter refused to cooperate with the Zentrum. The Zentrum, readier than the SPD to accept the stipulations of the ultimatum, now tried to form a government including both the DVP and the SPD. However, the DVP had voted against the ultimatum and a consensus proved impossible. Among those discussed as possible chancellors were Gustav Bauer and Paul Löbe (both SPD), Konrad Adenauer and Joseph Wirth (both Zentrum).