Count John Günther I was the son of the Count Günther Extra Large of Schwarzburg (1490–1552), nicknamed Günther the Rich or Günther with the large Jaws, and his wife Elisabeth (d 14 May 1572), a daughter of Count Philip of Isenburg-Büdingen-Ronneburg.
He is regarded as the progenitor of the line Schwarzburg-Sondershausen. John Günther I was raised as a Catholic and destined for an ecclesiastical career. He spent some time at the court of Elector Maurice of Saxony and fought in the Battle of Sievershausen on the side of Maurice against Albert Alcibiades, Margrave of Brandenburg-Kulmbach.
Maurice"s successor Augustus confirmed his tariff privilege on the salt trade in Frankenhausen.
He chose the city of Sondershausen as his residence. In 1571, the brothers decided to divide the County.
John Günther I"s part was named Schwarzburg-Sondershausen, after its capital.
