Wilhelm Filchner (13 September 1877 – 7 May 1957) was a German army officer, scientist and explorer. He conducted several surveys and scientific investigations in China, Tibet and surrounding regions, and led the Second German Antarctic Expedition, 1911–1913.

As a young military officer, Filchner gained an early reputation for dash and daring, following his travel exploits in Russia and the Pamir Mountains range. After further technical studies, he developed expertise in geography and geophysics, before leading a major scientific survey in Tibet and western China in 1903–1905. In 1909 he was appointed to organise and lead the forthcoming German expedition to the Antarctic, with both scientific and geographical objectives involving extensive exploration of the continent's interior. During the expedition his ship became trapped in the Weddell Sea ice, drifting for eight months and preventing Filchner from establishing a land base, thus failing in its main objective. Although important scientific results were obtained, the expedition was disrupted by serious interpersonal disagreements and lasting animosities, which harmed Filchner's reputation as a leader and ended his polar career.

After service in the First World War he resumed his travels in Asia. He conducted two lengthy single-handed magnetic surveys in China and Tibet, often in difficult and sometimes dangerous conditions, and was continuing this work when the Second World War began, leaving him stranded in India. After years of internment, he returned to Europe and retired to Zürich, where he died in 1957. During his lifetime he received numerous honours, including the German National Prize for Art and Science in 1937, and several honorary doctorates. He is also commemorated in the Antarctic, where a number of geographical features bear his name.

Wilhelm Filchner was born on 13 September 1877, the son of Eduard and Rosine Filchner. Sources place his birth variously at Munich or Bayreuth; it appears that the family moved from Munich to Bayreuth shortly after Wilhelm's birth, but returned to Munich after his father's early death. As a boy, Wilhelm showed considerable artistic and musical talent, drawing inspiration from, amongst others, Franz von Lenbach, Franz Stuck, and Siegfried Wagner. He might have made his life in the arts, but family traditions drew him towards a military career, and at the age of 15 he was enrolled in the Prussian Military Academy.

As a young officer in 1898, Filchner was given leave from the army to undertake a seven-week journey in Russia, but had to leave that country when he was suspected of acting as a spy. Two years later he made an expedition to the Pamir Mountains, which included a well-publicised horseback ride, travelling from Osh in the Fergana Valley to Murghab in Tajikistan, and returning by way of Kashgar in Sinkiang. During these travels, Filchner observed much Russian activity and noted the differences between the Russians and the English in their interactions with the indigenous people: "The Russians manage, in their dealings with Asiatic peoples, to reach out to their hearts, whereas the English, in their relations with natives, make a show of their cultural superiority". Through these adventures, which he recounted in a popular book, Ein Ritt über den Pamir ("A Ride over the Pamirs"), Filchner gained an early reputation as a daring traveller.

Back in Germany, Filcher developed his knowledge of geography and geophysics through courses at the Technical University of Munich and other institutions. Between 1900 and 1903, he formed contacts with some of the leading travelling scientists of the day, including the Swede Sven Hedin, and Ferdinand von Richthofen from the University of Berlin. In 1903, with von Richthofen's recommendation, the army gave him leave to assume the leadership of a major scientific survey in Tibet and western China, extending to the upper reaches of the Hwang Ho river. This was a potentially dangerous enterprise, and Filchner found it necessary at times to conceal his activities by disguising himself as a Muslim priest.

Filchner's principal scientific assistant on this journey was the geographer Albert Tafel, with whom relations were difficult and often strained. After the journey, Tafel missed few opportunities for insulting Filchner and undermining his authority as a leader, accusing him of cowardice and questioning the accuracy of his maps. Filchner's military background and formal manner contributed to the problem; as Cornelia Lüdecke puts it in a biographical essay on Filchner, as an officer he was "trained to command and not to discuss". This was a trait that would also be apparent in Filchner's later expeditions.

Filchner's interest in the Antarctic was sparked by the theories of Albrecht Penck of the University of Berlin, who considered that the then largely unexplored Antarctic continent comprised two separate landmasses, East and West Antarctica, divided by a strait connecting the Weddell and Ross Seas. Filchner wished to investigate this question, and in 1909, with the support of the Berlin Geographical Society, began preparations for an Antarctic expedition. He would not only test Penck's theory, but would combine geographical discovery with scientific inquiry. Filchner's original plan envisaged two ships, with shore parties advancing inland respectively from Weddell and Ross Sea bases, to meet in the vicinity of the Pole. This proved too costly, so Filchner had to adopt a more modest, single-ship strategy, confining his operations to the Weddell Sea area.