Thorvald Nicolai Thiele was born on December 24, 1838, and died on September 26, 1910. He was a Danish astronomer and the director of the Copenhagen Observatory. He was also an actuary and mathematician, best known for his work in statistics, interpolation, and the three-body problem.

Thiele made important contributions to the study of random time series in statistics. He introduced the concepts of cumulants and likelihood functions. Ronald Fisher, a famous statistician, called Thiele one of the greatest statisticians of all time. In the early 1900s, Thiele developed a voting method for elections with multiple winners called sequential proportional approval voting. This method was briefly used for party lists in Sweden when proportional representation was introduced in 1909.

Thiele was a founder and mathematical director of the Hafnia Insurance Company. He also helped establish the Danish Society of Actuaries. His work in insurance led him to collaborate with mathematician Jørgen Pedersen Gram.

Thiele was the father of Holger Thiele, who was also an astronomer.

Two main-belt asteroids, 843 Nicolaia (discovered by his son Holger) and 1586 Thiele, are named in his honor.

Selected publications

• A book about using the least squares method to correct some systematic errors. 1880.
• A book about how to make accurate measurements. 1903.
• A book about interpolation methods. 1909.