Robert Endre Tarjan (born April 30, 1948) is an American computer scientist and mathematician.

His father, George Tarjan (1912-1991), raised in Hungary,[1] was a child psychiatrist, specializing in mental retardation, and ran a state hospital.

[3] As a child, Robert Tarjan read a lot of science fiction, and wanted to be an astronomer.

At Stanford, he was supervised by Robert Floyd[5] and Donald Knuth,[6] both highly prominent computer scientists, and his Ph.D. dissertation was An Efficient Planarity Algorithm.

Tarjan has worked at AT&T Bell Labs (1980–1989), Intertrust Technologies (1997–2001, 2014–present), Compaq (2002) and Hewlett Packard (2006–2013).

Another significant contribution was the analysis of the disjoint-set data structure; he was the first to prove the optimal runtime involving the inverse Ackermann function.

The citation for the award states[10] that it was: For fundamental achievements in the design and analysis of algorithms and data structures.Tarjan was also elected an ACM Fellow in 1994.