Patricia Ann Thiel (February 20, 1953 – September 7, 2020) was an American chemist and materials scientist who served as a distinguished professor of chemistry at Iowa State University.

After working for a year at Control Data Corporation as an analytic chemist, she enrolled in the chemistry department at the California Institute of Technology, with financial support from a National Science Foundation Predoctoral Fellowship.

[3][4][5] Thiel's first appointment after graduation was as an Alexander von Humboldt Fellow at the Ludwig Maximilian University of Munich, where she worked in the research group of Gerhard Ertl, who later went on to receive the 2007 Nobel Prize in Chemistry.

[8] Thiel's research elucidated atomic-scale structures and processes on solid surfaces, in areas relevant to microelectronics, tribology, heterogeneous catalysis, and nanoscience.

[17] She was the co-author, along with Theodore E. Madey, of a highly cited and comprehensive review article describing the interactions and properties of water near solid surfaces.

[25][26] Because of this mechanism, they predicted an unusual variation in film roughness with temperature from theory, and eventually confirmed it experimentally using Scanning Tunneling Microscopy.

[30][31][32] She and her collaborators also discovered that metallic nanoparticles can be grown as encapsulated clusters near the surface of a layered material, graphite, if specific growth conditions are met.