Yuan Tseh Lee (Chinese: 李遠哲; pinyin: Lǐ Yuǎnzhé; Wade–Giles: Li³ Yüan³-che²; Pe̍h-ōe-jī: Lí Oán-tiat; born 19 November 1936) is a Taiwanese chemist.

[4] Lee was born to a Hoklo Taiwanese family in Shinchiku City (modern-day Hsinchu city) in northern Taiwan, which was then under Japanese rule, to Lee Tze-fan, an artist, and Ts'ai P'ei (蔡配; Cài Péi), an elementary school teacher from Goseikō Town (梧棲港街), Taichū Prefecture (Wuqi, Taichung).

[7] One of the major goals of chemistry is the study of material transformations where chemical kinetics plays an important role.

Swedish chemist Svante Arrhenius studied this phenomenon during the late 1880s, and stated the relations between reactive molecular encounters and rates of reactions (formulated in terms of activation energies).

Other scientists at the time also stated a chemical reaction is fundamentally a mechanical event, involving the rearrangement of atoms and molecules during a collision.

In the 1950s, 1960s and 1970s, with the development of many sophisticated experimental techniques, it became possible to study the dynamics of elementary chemical reactions in the laboratory.

In 2010, Lee said that global warming would be much more serious than scientists previously thought, and that Taiwanese people needed to cut their per-capita carbon emissions from the current 12 tons per year to just three.

[11] At the request of president Chen Shui-bian, Lee was Taiwan's representative in the 2002 APEC leaders' summit in Mexico.

[12] In July 2024, Lee accepted president Lai Ching-te's invitation to serve as a consultant on the newly formed National Climate Change Strategy Committee.

His elder brother Yuan-Chuan Lee has been a professor at Johns Hopkins University for 40 years and was awarded the honor Special Chair Lectureship in Academia Sinica in Taiwan.

In January 2004, he and industrial tycoon Wang Yung-ching and theatre director Lin Hwai-min issued a joint statement to both Chen Shui-bian and Lien Chan.

He backed Chen again in the 2004 elections, issuing a statement of support for the DPP on 17 March, three days before polls opened.

[20] Yuan Tseh Lee was awarded the Othmer Gold Medal in 2008 in recognition of his outstanding contributions to progress in chemistry and science.