Lothar Siegfried Freiherr von Richthofen (27 September 1894 – 4 July 1922) was a German First World War fighter ace credited with 40 victories. He was a younger brother of top-scoring ace Manfred von Richthofen (the Red Baron) and a distant cousin of Luftwaffe Field Marshal Wolfram von Richthofen, who also became a flying ace.
Following the war, Lothar worked for a while on a farm before taking an industrial position. He married in June 1919 and had two children. Yearning for aviation, he accepted a position as a pilot, conveying passengers and postal mail between Berlin and Hamburg.