Peter I or Peter Frederick Louis of Holstein-Gottorp (German: Peter Friedrich Ludwig von Holstein-Gottorp) (17 January 1755 – 21 May 1829) was the Regent of the Duchy of Oldenburg for his incapacitated cousin Peter Frederick William from 1785 to 1823, and then served himself as Duke from 1823-1829.

He also served from 1785 to 1803 as the last Lutheran Prince-Bishop of Lübeck, until that Prince-Bishopric was secularized and joined to Oldenburg. His son, Augustus, was the first Duke of Oldenburg to use the style of Grand Duke that was granted in 1815.

Peter Frederick Louis was born on 17 January 1755 at Riesenburg. He was the only surviving son of Prince Georg Ludwig of Holstein-Gottorp and Sophie Charlotte of Schleswig-Holstein-Sonderburg-Beck.

On 6 June 1781, he married Duchess Frederica of Württemberg, the second daughter of Frederick II Eugene, Duke of Württemberg and his wife, Friederike Dorothea of Brandenburg-Schwedt. They had two sons: August (born in 1783) and George (born in 1784).

Fredericka died due to complications from a miscarriage on 24 November 1785 at Vienna, Austria, predeceasing her husband by forty years.

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