For the founder of the Right Livelihood Award, see Jakob von Uexkull.

Jakob von Uexküll (September 8, 1864 - July 25, 1944) was an Estonian biologist who had important achievements in the fields of muscular physiology and the cybernetics of life. However, his most notable achievement is the notion of Umwelt, used by semiotician Thomas Sebeok.

Von Uexküll was interested in how living beings subjectively perceive their environment. Picture, for example, a meadow as seen through the compound eyes of a fly, and then again as seen in black and white by a dog, and heard in a wider range of sounds. Von Uexküll called these subjective worlds Umwelt.

His writings show an excitement with the multiplication of wonderful worlds that ensues from considering the Umwelt of different creatures. This feature gives some of his writings a poetical quality.

Studies upon von Uexküll, such as those by Kalevi Kull, connect von Uexküll's studies with some areas of philosophy such as phenomenology and hermeneutics. Von Uexküll's work is both interesting and influential to various fields of knowledge. He is a pioneer of semiotic biology, or biosemiotics. However this thinker is not widely known or translated from German.