Otto IV of Schaumburg (1517 – 21 December 1576) was a German nobleman. He was a ruling Count of Schauenburg and of Holstein-Pinneberg. He was a son of Jobst I and his wife Mary of Nassau-Siegen, a daughter of Count John V of Nassau-Siegen.

He adopted the teachings of Martin Luther. However, with respect to his elder brothers Cologne's Archbishop-Electors Adolphus III (reg. 1547–1556) and Anthony I (reg. 1557–1558) he refrained from open confrontation. In 1559 he officially began the Reformation in Schauenburg and Holstein-Pinneberg. These areas remained Lutheran throughout the Counter-Reformation and into modern times.

Marriages and issue

Otto first married Mary (*1527–1554*), daughter of Duke Barnim XI of Pomerania-Stettin. Mary and Otto had four sons:

• Hermann (*1545–1592*), Prince-Bishop of Minden (1566–1581)
• Otto (*1545–1572*), (mentally insane)
• Adolphus XIV (*1547–1601*), count regnant in Schaumburg and Holstein-Pinneberg. married to Elisabeth of Brunswick-Wolfenbüttel (1567–1618).
• Anthony (*1549–1599*), Prince-Bishop of Minden (1587–1599)

In 1558 Otto married a second time, with Elisabeth Ursula (*1539–1586*), a daughter of Ernest I, Duke of Brunswick-Lüneburg. Elisabeth Ursula and Otto had two daughters and one son:

• Mary (*1559–1616*) married in 1591 Count Josse of Limburg-Styrum (*1560–1621*)
• Elisabeth, married in 1585 Count Simon VI of Lippe (*1554-1613*)
• Ernest (*1569–1622*), count regnant of Schaumburg and Holstein-Pinneberg as of 1601, elevated to Prince of Schaumburg in 1619.