Gheorghe Țițeica (Romanian pronunciation: [ˈɡe̯orɡe t͡siˈt͡sejka]; 4 October 1873 in Turnu Severin – 5 February 1939) publishing as George or Georges Tzitzeica) was a Romanian mathematician with important contributions in geometry. He is recognized as the founder of the Romanian school of differential geometry.

He showed an early interest in science, as well as music and literature. Țițeica was an accomplished violinist, having studied music since childhood: music was to remain his hobby. While studying at the Carol I High School in Craiova, he contributed to the school's magazine, writing the columns on mathematics and studies of literary critique. After graduation, he obtained a scholarship at the preparatory school in Bucharest, where he also was admitted as a student of the mathematics department of the Faculty of Sciences. In June 1895, he graduated with a Bachelor of Mathematics.

In the summer of 1896, after a stint as a substitute teacher at the Bucharest theological seminary, Țițeica passed his exams for promotion to a secondary school position, becoming teacher in Galaţi.

In 1897, on the advice of teachers and friends, Țițeica completed his studies at a preparatory school in Paris. Among his mates were Henri Lebesgue and Paul Montel. On June 30, 1899 he defended his doctoral thesis titled Sur les congruences cycliques et sur les systemes triplement conjugues, on the framework of oblique curvature, before a board of examiners led by Gaston Darboux.

Upon his return to Romania, Țițeica was appointed assistant professor at the University of Bucharest. He was promoted to full professor on 4 May 1900, retaining this position until his death in 1939. He also taught mathematics at the Polytechnic University of Bucharest. In 1913, at age 40, Țițeica was elected as a permanent member of the Romanian Academy, replacing Spiru Haret. Later he was appointed in leading roles: in 1922, vice-president of the scientific section, in 1928, vice-president and in 1929 secretary general. Țițeica was also president of the Mathematical Association of Romania, of the Romanian Association of Science and of the Association of the development and the spreading of science. He was a vice-president of the Polytechnics Association of Romania and member of the High Council of Public Teaching.

Țițeica was elected correspondent of the Association of Sciences of Liège and doctor honoris causa of the University of Warsaw. He was the president of the geometry section at the International Congress of Mathematicians in Toronto (1924), Zürich (1932), and Oslo (1936). In 1926, 1930 and 1937 he gave a series of lectures as titular professor at the Faculty of Sciences in Sorbonne. He also gave many lectures at the University of Brussels (1926) and the University of Rome (1927).

Țițeica wrote about 400 articles, of which 96 are scientific projects, most addressing problems of differential geometry. Carrying on the researches of the American geometer of German origin Ernest Wilczynski, Țițeica discovered a new category of surfaces and a new category of curves which now carry his name; his contributions represent the beginning of a new chapter in mathematics, namely the affine differential geometry. He also studied R-networks in n-dimensional space, defined through Laplace equations.

Țițeica had three children, the youngest of whom was the physicist Șerban Țițeica.