Branislav Petronijević (Serbian Cyrillic: Бранислав Петронијевић; also spelled Petronievics; 6 April 1875 – 4 March 1954) was a Serbian philosopher and paleontologist, and a professor at the University of Belgrade. He is regarded as one of the most prominent Serbian philosophers of the first half of the 20th century and played a central role in the institutionalization of academic philosophy in Serbia and Yugoslavia.

Trained in Vienna and Leipzig under figures such as Ludwig Boltzmann, Johannes Volkelt and Wilhelm Wundt, Petronijević developed an original metaphysical system that he called "monopluralism", a synthesis of Spinoza's substance monism and Leibniz's monadological pluralism shaped by the idealist tradition of Hermann Lotze and Eduard von Hartmann. In his self-described "empirio-rationalist" epistemology he held that immediate experience both presents reality as it is and yields the basic logical and metaphysical axioms, including the principle of sufficient reason, from which he sought to derive an "absolute metaphysics". His major systematic works, notably Prinzipien der Metaphysik (Principles of metaphysics, 1904–1911), develop a discrete, finitist conception of space built from simple qualitative points, a "hypermetaphysics" concerned with the most general oppositions of the One and the Many, and a broader program that also encompasses the foundations of mathematics, experimental psychology, aesthetics, and practical philosophy.

Alongside his metaphysical and epistemological writings, Petronijević made contributions to the philosophy of science and to natural history, publishing on universal evolution and proposing an interpretation of Dollo's law as well as what he called the Law of Non-correlative Evolution. In paleontology he was among the early specialists on Archaeopteryx, introducing the genus Archaeornis and several related names. However, later work has generally not adopted these taxonomic arrangements.

A participant in the Serbian army's Great Retreat in World War I, he served as a war correspondent, lectured in Paris and London, and wrote the biographical preface to the 1922 English edition of Roger Joseph Boscovich's A Theory of Natural Philosophy. He was a full member and later secretary of the Serbian Academy of Sciences and Arts, co-founded the Serbian Philosophical Society, mentored the philosopher Ksenija Atanasijević, and was nominated for the Nobel Prize in Literature in 1941 and 1947.

Branislav Petronijević was born in the small village of Sovljak, near Ub, Serbia, on 6 April (25 March, O.S.) 1875, the son of Marko Jeremić, a theologian. The last name Petronijević stems from Branislav's grandfather, Petronije Jeremić, a local priest. His father changed Branislav's last name to reduce pressure at school, as the Jeremić family were prominent supporters of the exiled Karađorđević dynasty.

He studied at the Valjevo Gymnasium and the Grande école in Belgrade (the Belgrade Higher School).

In 1894, Petronijević went to Vienna to pursue a degree in medicine, on a scholarship awarded by the Tamnava srez. Petronijević joined the Philosophical Society of the University of Vienna and studied under Ludwig Boltzmann. After three semesters in Vienna he enrolled at the University of Leipzig, where he studied philosophy under Johannes Volkelt, Wilhelm Ostwald, and Ernst Mach. There, he wrote Der ontologische Beweis für das Dasein des Absoluten (The ontological proof for the existence of the absolute) in 1897, and successfully defended his thesis Der Satz vom Grunde (The principle of sufficient reason) in 1898. Having studied during this time under Wilhelm Wundt, Petronijević later published several works in experimental psychology on the observation of the transparent and on the depth and observation of compound colours. In Leipzig, Petronijević received financial help from former bishop Nikanor Ružičić, with whom he practiced the German language.

In 1898 he was given the title of docent at the Belgrade Higher School at the request of professor Ljubomir Nedić. He taught the German language and philosophical propaedeutics at the Third Belgrade Gymnasium. Petronijević was promoted to the post of associate professor in 1899, and then full professor in 1903. Three years later when the school developed into the University of Belgrade, Petronijević was demoted back to associate professor. He was simultaneously elected correspondent member of the Serbian Royal Academy on 3 February 1906. Petronijević found this humiliating, and declined the post, his decision coming into effect in 1910. During this time, Petronijević also taught art theory at Rista and Beta Vukanović's Serbian Art School in Belgrade.