Aleksander Lesser was a Polish painter, illustrator, sketch artist, art critic, and amateur researcher of antiquities who was of Jewish descent. Lesser holds a place in Polish art history "as an outstanding representative of his country’s historical school." He specialized in Polish historical and contemporary themes, and he was known and respected in artistic and scholarly circles. He was a member of Kraków's Academy of Learning and co-founder of Warsaw's Zachęta, the Society for Encouragement of the Fine Arts.

Aleksander Lesser was born in Warsaw in 1814 to Levy Lesser (1791–1870), a famous trader and banker, and Roza Loewenstein (1790–1840). Lesser's formal study of painting began in the Warsaw Lyceum under Aleksander Kokular before continuing at the Faculty of Fine Arts at the Royal University of Warsaw in 1830–1831 under Antoni Brodowski, the Polish romantic painter. This university was closed by the imperial Russian authorities after the Polish uprising of 1831; thus, between 1832 and 1835, Lesser continued his studies at the Academy of Fine Arts in Dresden, where he studied with Moritz Retzsch and Karl Christian Vogel. Between 1836 and 1846, Lesser studied in Munich under Peter Cornelius, Heinrich Hess, and Julius Schnorr von Carosfeld; these individuals were prominent representatives of German romanticism who called themselves Nazarenes. In 1843, Lesser became friends with a prominent Polish poet named Cyprian Kamil Norwid (Norwid later emigrated).

Lesser returned to Warsaw in 1846, where he was widely praised for his treatment of historical and religious (primarily Christian) themes, as well as for his portraits and genre scenes. Many of his paintings, including Obrona Trembowli (The Defense of Trembowla; 1840), were interpreted by both critics and the public as allegories of the Polish struggle for independence.

Lesser began giving a more important role to Jewish themes in his work in the 1860s, thus becoming one of the first artists to paint scenes from modern Polish Jewish history. In addition, Lesser began painting and sketching scenes from Polish Jewish history upon the encouragement of Joachim Lelewel, a historian and advocate of Polish independence who was living in exile. In 1860, Lesser was a co-founder of the Society for the Encouragement of the Fine Arts, an organization which aimed to promote art for the mutual benefit of both artists and society at large (and which still exists to this day).

Lesser was a member of the executive committee of this organization from 1864 to 1883, and he served on the Commission on Art History in the Academy of Arts and Sciences in Kraków starting from 1878. Lesser died in 1884 at the age of 69. Nowadays, his works are mostly located in the National Museum in Warsaw (more than 436 drawings and sketches), in the National Museum in Kraków, and in collections in Poznań and Lviv.