The House of Schleswig-Holstein-Sonderburg-Beck (Schleswig-Holstein-Beck or Beck for short) was a line of the Schleswig-Holstein-Sonderburg branch of the House of Oldenburg. It consisted of August Philipp, Duke of Schleswig-Holstein-Sonderburg-Beck (1612–1675) and his male-line descendants. Schleswig-Holstein-Glücksburg, to which several present-day royal houses belong, is the new name of Schleswig-Holstein-Beck.

Coat of arms of the Dukes of Schleswig-Holstein-Sonderburg-Beck

The members of the line were titular dukes of Schleswig and Holstein, and they were originally not ruling. The line is named after Beck, a manor in Ulenburg, Bishopric of Minden (today Löhne, North Rhine Westphalia). August Philipp bought this manor from the Count of Oldenburg, and he made it his residence.

Family tree of the Dukes of Schleswig-Holstein-Sonderburg-Beck (tenure as duke is shown in brackets):