design: This study determined the chloroplast genome sequence of Cyperus eragrostis Lam., which is well known as an ornamental plant but is commonly recognized as a weed in introduced regions. The chloroplast genome of C. eragrostis was found to be 184,646 bp in total length, featuring a quadripartite structure comprising a large single-copy (LSC) region (101,639 bp), a small single-copy (SSC) region (11,231 bp), and two inverted repeat (IR) regions (35,888 bp). The genome contained a total of 132 genes, including 87 CDSs, 37 tRNAs, and 8 rRNAs. Maximum likelihood (ML) analysis was conducted using 75 CDSs extracted from the chloroplast genomes of 19 related species. The analysis revealed that C. eragrostis has the closest relationship with C. difformis. The results of this study are expected to serve as fundamental data for various academic fields, including phylogenetic and evolutionary studies of the Cyperus genus.