Born in Algringen (today, Algrange) in Alsace-Lorraine to a coal miner and his wife, Wagner attended Volksschule locally and Realschule in Metz and Pforzheim.

In an incident in January 1932, Wagner was sentenced by a court to a fine of 250 ℛ︁ℳ︁ or ten days in jail for assaulting a journalist on the floor of the Landtag.

He advocated the establishment of special protective custody facilities that resulted in Heinrich Himmler, then Acting Police President in Munich, soon setting up the first Nazi concentration camp in Dachau.

He thus wielded enormous power in both the party and the government, despite nominally reporting to Reichsstatthalter (Reich Governor) Franz Ritter von Epp.

[10] In May 1934, Wagner secured an appointment on the staff of Deputy Führer, Rudolf Hess to head a task force charged with reform of the Reich structure.

By February 1935, Wagner produced a lengthy report titled "Reconstruction of the Reich" calling for the placement of all legislative and executive decision-making power in the hands of Party officials, leaving the State authorities as mere administrative entities.

[13] A few months later, during the Kristallnacht pogrom of 9-10 November 1938, rampaging Nazis also destroyed other historic synagogues throughout the city and looted Jewish shops.

[16] Despite this setback, Hitler apparently remained on good terms with Wagner, one of the Alter Kämpfer and holder of the Golden Party Badge.

Confident of his close ties with Hitler, Wagner openly boasted that he often ignored directives from Reichsministers, and that if they wanted to consult with him on issues, they would have to schedule a visit to Munich.

[19] At the outbreak of the Second World War on 1 September 1939, Wagner was named Reich Defense Commissioner for Wehrkreise (Military Districts) VII and XIII.

[16] Wagner for many years suffered from the effects of chronic alcoholism, and his condition worsened in November 1941 after follow-up operations for his WWI leg injury.

Wagner nominally remained in his posts until a second stroke resulted in his death on 12 April 1944, at which time Giesler was named his permanent successor.

The increasingly reclusive Führer made a rare public appearance to attend Wagner's lavish funeral on 17 April at the Deutsches Museum that included a eulogy by Minister of Propaganda Joseph Goebbels.