Wei Dongyi (; born 1992 in Jinan, Shandong) is a Chinese mathematician who is currently serving as associate professor and assistant researcher at the School of Mathematical Science in Peking University.
He has attracted attention on Chinese social media for his simple living style. In 2021, he was called Peking University's "ugliest teacher" due to his unkempt appearance.
Wei Dongyi graduated from Attached Senior School of Shandong Normal University and began studying at Peking University in 2010, then earned his bachelor's degree in 2014 and PhD in 2018 under Tian Gang as his doctoral advisor. His research field includes partial differential equations and differential geometry.
In December 2019, Wei completed his post-doctoral work and became an assistant professor in the Mathematics Department of Peking University. In November 2025, he became an associate professor of the university.
Wei Dongyi became viral on the internet from a street interview in May 2021 when he was seen dressed in an unassuming manner, holding a large bottle of drinking water and a bag of mantou (steamed buns). His appearance has led to netizens dubbing him the "sweeping monk" of Peking University.
A group of doctorate mathematicians had been struggling to build a mathematical model for months and called Wei Dongyi for help. He provided equations to alter their experiment which resulted in the mathematical model obtaining a 96% passing rate. The mathematicians wanted to pay the professor to show their gratitude, but he declined. "ItâÂÂs unnecessary to pay me for such an easy problem," he said. Wei eventually asked for a recharge of his transport card as a form of compensation.
Wei Dongyi is nicknamed âÂÂGod Weiâ (é¦ç¥Â) by Chinese netizens.