Lu Jiaxi (simplified Chinese: 陆家羲; traditional Chinese: 陸家羲; pinyin: Lù Jiāxī; June 10, 1935 – October 31, 1983) was a self-taught Chinese mathematician who made important contributions in combinatorial design theory. He was a high school physics teacher in a remote city and worked in his spare time on the problem of large sets of disjoint Steiner triple systems.

Lu Jiaxi was born in a poor family in Shanghai. His father was a seller of soy sauce concentrate. His parents had four children, but the three older children all died early from illness, and Lu Jiaxi was the only surviving child.

When he was in junior middle school, his father died from an illness that the family could not afford to treat, so he started working after finishing junior middle school in 1949 to earn a living. He served an apprenticeship at an automobile hardware firm in Shanghai. In October 1951, he was admitted to a statistics training course in Shenyang offered by the administration for electrical equipment industry of Northeast China, and he finished first in his class. He was then assigned to a motor factory in Harbin.

While working at the factory, he self-studied high school materials. He also learned Russian at a night school, and later English and Japanese to be able to look up literature. In 1956, he joined the fight against the flooding of Songhua River, for which he was commended. In 1957, he passed the college entrance exam and was admitted to Department of Physics of Jilin Normal University, now called Northeast Normal University (not the university that took the same name in 2002).

After graduation in 1961, he was assigned to Baotou Steel and Iron Institute, now called Inner Mongolia University of Science and Technology, as a teaching assistant. In 1962, after reorganization of the institute, he was assigned first to the Teaching and Research Office of Baotou Education Bureau, then to several middle schools in Baotou as a physics teacher. He worked at Baotou Eighth Middle School, Baotou Fifth Middle School, Baotou Twenty-fourth Middle School from 1965 to 1973, and Baotou Ninth Middle School from 1973 to his death in 1983. Because of his physics background and his past experience as a factory worker, he was also in charge of a school-run factory which produced radio components. He married in the summer of 1972 to a doctor introduced by his colleague.

In the summer of 1956, he read a popular science book on mathematical problems written by Chinese mathematician Sun Zeying (Chinese: 孙泽瀛, published under the name J. Tseying Sun) called Shuxue Fangfa Qu Yin (Chinese: 數學方法趣引; lit. 'Interesting introduction to mathematics methods') and was fascinated by the Kirkman's schoolgirl problem. He devoted himself into solving the generalized version of the problem, studying relevant areas in mathematics on his own and spending a lot of time on research.

In December 1961, he wrote up a paper on its solution and another paper on Latin squares and sent them to Institute of Mathematics of the Chinese Academy of Sciences. The reply letter came in February 1963. They did not directly comment on the papers but suggested that he check them himself and send them to journals if the results were new. They also included some references on the latest developments. He revised his paper on the generalized Kirkman's schoolgirl problem and submitted it to Shuxue Tongbao (Chinese: 数学通报; lit. 'Bulletin of mathematics') in March 1963. His paper was too long and technical for the journal, which aimed at middle school teachers. However, it took the journal one year to reply to him, stating that he should submit it elsewhere. After further revisions, he submitted the paper to Acta Mathematica Sinica on March 14, 1965. On February 7, 1966, he received the rejection letter from the journal criticizing it as "basically not really new results, worthless". It was realized after his death that this rejection was a serious mistake. In 1966, he sent two other papers to journals with no response, since with the start of the Cultural Revolution all academic activities were disrupted. He was discouraged by the rejections and wrote in his diary that he "had since then given up the thought of submitting papers".

After the Cultural Revolution, he resubmitted some revised papers, but they were not accepted. In April 1979, in some journal issues of 1974 and 1975 that he managed to borrow from Beijing, he unexpectedly learned from a paper of Haim Hanani that the problem which he solved in his 1965 paper had been solved and first published in 1971 by Ray-Chaudhuri and R. M. Wilson, which was a big blow to him.