Abstract: Lactylation is a novel lactate-dependent post-translational modification that can alter the structure and function of proteins by covalently coupling lactoyl groups to lysine residues. Therefore, gene expression is regulated and lactylation participates in cellular metabolic and growth processes. Recent studies have shown that lactylation in tumor tissues can affect tumor occurrence and development by regulating intracellular signal transduction, gene expression, and protein function. This review summarizes the discovery process of lactylation and recent research progress in tumors, providing novel insights into their prevention and treatment.