Euler married Katharina Gsell, the daughter of Georg Gsell, a painter and director of the Imperial Art Gallery in St. Petersburg. They formed a close and supportive partnership.

Euler and Katharina had thirteen children together, but only five survived to adulthood: Johann Albrecht, Karl, Christoph, Charlotte, and Helene. He was a devoted father and took a keen interest in his children's education.

Euler maintained correspondence and collaborated with numerous scientists and mathematicians, including the Bernoulli family (Johann, Daniel, and Nicolaus), Christian Goldbach, and Joseph-Louis Lagrange. He was known for his generosity in acknowledging and supporting the work of others.

Leonhard Euler suffered the loss of his beloved wife Katharina Gsell.

A year after the passing of Katharina Gsell, Leonhard Euler remarried her half-sister, Salome Abigail Gsell. This marriage ensured the continued care of his children and household.