We present a genome assembly of Polygonum maritimum (Sea Knotgrass; Streptophyta; Magnoliopsida; Caryophyllales; Polygonaceae). The genome sequence has a total length of 428.64 megabases. Most of the assembly (99.95%) is scaffolded into 10 chromosomal pseudomolecules. The mitochondrial sequence has a length of 352.4 kilobases and the plastid genome assembly has a length of 163.31 kilobases. This assembly was generated as part of the Darwin Tree of Life project, which produces reference genomes for eukaryotic species found in Britain and Ireland.
