Polyploidy defines eukaryotic cells with more than two sets of homologous chromosomes. Polyploid animal genome assemblies have restricted homologous chromosome copies to a "mosaic" ("collapsed") representation. Using cutting-edge long-read sequencing and 3D-technologies, we deciphered the genome of an invasive Eurasian teleost fish species, the asexual Prussian carp, and present the first haplotype-resolved chromosome-scale assembly of a hexaploid animal in unprecedented contiguity and completeness. Assembly of all 150 chromosomes revealed genomic structure, phylogeny and genome duplication history.