Elisabeth Sophie of Brandenburg, was a Duchess consort of Courland, Margravine consort of Brandenburg-Bayreuth and Duchess consort of Saxe-Meiningen.

She was married to:

• Duke Frederick Casimir Kettler of Courland,
• Christian Ernst, Margrave of Brandenburg-Bayreuth, and
• Ernst Ludwig I, Duke of Saxe-Meiningen.

She was joint regent in Courland during the minority of her son from 1698 until 1701.

Elisabeth Sophie was born to Frederick William I, Elector of Brandenburg and Sophia Dorothea of Schleswig-Holstein-Sonderburg-Glücksburg.

She married (29 April 1691) to her cousin, Duke Frederick Casimir Kettler of Courland (1650–1698).

The marriage was arranged as an alliance between the two families; in 1703 her brother Albert Frederick was to marry her first husband's daughter Mary Dorothea. When her husband died in 1698, Elisabeth Sophie became joint guardian-regent alongside with her former brother-in-law Ferdinand.

In January 1701, Elisabeth Sophie left Courland, her son and former stepdaughter for her brothers court in Berlin.

In 1703, she was formally deprived of the custody of her son and the regency. She was later given a Russian allowance from Anna of Russia.

She married Christian Ernst, Margrave of Brandenburg-Bayreuth (6 August 1644 – 20 May 1712) on 30 March 1703 in Potsdam.

She is said to have dominated her second spouse completely and directed his policy in a pro-Prussian direction. He gave her the palace Markgräfliches Schloss Erlangen, which was named after her. She was described as proud and a great lover of pomp and ceremony. Her expenses had a bad effect on the finances of the state.

She married on 3 June 1714 on Schloss Ehrenburg to Ernst Ludwig I, Duke of Saxe-Meiningen (1672–1724).