Thomas J. Jech (Czech: Tomáš Jech, pronounced [ˈtomaːʃ ˈjɛx]; born 29 January 1944 in Prague) is a mathematician specializing in set theory who was at Penn State for more than 25 years.

He was educated at Charles University (his advisor was Petr Vopěnka) and from 2000 is at the Institute of Mathematics of the Academy of Sciences of the Czech Republic.

Jech's research also includes mathematical logic, algebra, analysis, topology, and measure theory.

Jech gave the first published proof of the consistency of the existence of a Suslin line. With Karel Prikry, he introduced the notion of precipitous ideal. He gave several models where the axiom of choice failed, for example one with ω₁ measurable. The concept of a Jech–Kunen tree is named after him and Kenneth Kunen.

• "Non-provability of Souslin's hypothesis", Comment. Math. Univ. Carolinae, 8: 291–305, 1967, MR 0215729
• Lectures in set theory, with particular emphasis on the method of forcing, Springer-Verlag Lecture Notes in Mathematics 217 (1971) (ISBN 978-3540055648)
• The axiom of choice, North-Holland 1973 (Dover paperback edition ISBN 978-0-486-46624-8)
• (with K. Hrbáček) Introduction to set theory, Marcel Dekker, 3rd edition 1999 (ISBN 978-0824779153)
• Multiple forcing, Cambridge University Press 1986 (ISBN 978-0521266598)^[1]
• Set Theory: The Third Millennium Edition, revised and expanded, 2006, Springer Science & Business Media, ISBN 3-540-44085-2. 1st ed. 1978;^[2] 2nd (corrected) ed. 1997

• Home page Archived 2012-05-04 at the Wayback Machine, with a copy at Penn state.
• Thomas Jech at the Mathematics Genealogy Project