Masatoshi Takeichi (竹市　雅俊, Takeichi Masatoshi, born November 27, 1943) is a Japanese cell biologist known for his identification of the cadherin class of adhesion molecules, which plays important roles in the construction of tissues. He shared the 2005 Japan Prize with Erkki Ruoslahti for "fundamental contribution in elucidating the molecular mechanisms of cell adhesion". He was selected as a Member of the Japan Academy (MJA) in 2000 and as a Foreign Associate of the United States National Academy of Sciences.