Wilhelm Altheim was a German painter and etcher of the 19th and 20th centuries in Hesse.

Wilhelm Altheim was the younger brother of Georg Altheim. Altheim was a student of J. H. Hasselhorst from 1886 to 1890 and of Frank Kirchbach at the Städelsches Kunstinstitut in Frankfurt am Main from 1890 to 1894. Altheim initially lived in Eschersheim near Frankfurt and from 1895 in Frankfurt.

This was followed by study visits: 1894 in Paris, 1904/05 in Italy and elsewhere, 1907 in Holland, 1909 in the south of France. Altheim returned to Frankfurt in 1912.

Altheim was a member of the "Freie Vereinigung Darmstädter Künstler" and the "Verband der Kunstfreunde in den Ländern am Rhein". At times he received an honorary salary from the latter association.

Influenced by Pidoll, Altheim painted nature and people from his immediate surroundings and closer home with a monumental tendency, especially landscapes from afar, portraits, historical and religious motifs, as well as peasant and soldier scenes (drawings, watercolors, oil paintings, tempera and also mixed media). After 1900, inspired by B. Mannfeld, he also worked as an etcher (e.g. The Shepherds of Bethlehem, etching from 1912 in the Karl August Reiser Collection, Bonn). Some of his 35 plates (mainly created after 1908) are monogrammed with W. A., others with A. A.. His drawings are still highly valued among collectors in the Rhine-Main region.