Euler accepted a position at the St. Petersburg Academy of Sciences, initially in the department of medicine and physiology, due to a surplus of mathematicians at the time. He was recommended by Daniel and Nicolaus Bernoulli.

Euler became a professor of physics at the Academy, marking his shift towards core scientific disciplines.

Euler succeeded Daniel Bernoulli as the head of the mathematics department at the Academy, solidifying his leading role in mathematics.

Euler married Katharina Gsell, the daughter of Georg Gsell, an artist from the Academy. They would eventually have thirteen children, though only five survived infancy.

Euler solved the famous Basel problem, finding the exact sum of the reciprocals of the squares of positive integers (ζ(2) = π²/6). This accomplishment brought him widespread recognition.

Euler began to experience vision problems, possibly due to overwork and the strain of his intensive mathematical research. He lost sight in his right eye during this period.