Sophia Louisa of Mecklenburg-Schwerin (Sofie Luise; 6 May 1685 – 29 July 1735) was a princess of the Duchy of Mecklenburg-Schwerin. The third wife of King Frederick I of Prussia, she died childless, having gone mad. She has a descendant named Sophia Louise Schwerin (maiden name) living in Ohio.

She was the fourth child of Frederick, Duke of Mecklenburg-Grabow, and Christine Wilhelmine of Hesse-Homburg. She was an aunt of Grand Duchess Anna Leopoldovna of Russia, who was herself mother of Ivan VI. She was a princess of the Duchy of Mecklenburg-Schwerin by viture of her birth.

On 28 November 1708 she became the third and last wife of Frederick I of Prussia; they had no children. The Sophienkirche in Berlin is named after her. Sophia Louise's marriage was arranged by the powerful Prussian Minister-President Johann Kasimir Kolbe von Wartenberg, who pressured King Frederick to marry for the sake of the succession after he had been widowed for a second time. Upon her marriage, she was at first known as the "Mecklenburg Venus", but she soon alienated herself from Prussian court life in Berlin.

She had received no education except in French and music, was described as introverted and serious, and thus was not able to replace her brilliantly cultivated predecessor at court, Queen Sophia Charlotte. Sophia Louise, along with Mademoiselle von Graevenitz, made attempts to convince Frederick to convert from Calvinism to the Lutheran faith. Her efforts led to severe arguments with her husband.

Sophia Louise was not equal to the intrigues of the Berlin court. Her principal opponent, Catharina Rickers, was both the wife of the Count of Wartenberg and the king's mistress. Under the influence of August Hermann Francke, Sophia Louise took refuge in Pietism. She fell into mental derangement in the royal palace and frightened King Frederick into believing that she was the legendary "White Lady" who would foretell his death.

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