A genome map is a table or diagram which shows the locations, in a genome, of a number of unique markers.

These markers act as reference points to help in navigating around the genome, much as chapter-headings help in navigating a book. By this analogy, the complete text of the book would be the genome sequence.

Genome maps underpin most genome sequencing: the mapped markers act as a scaffold around which to build up the sequence. Maps are also used to help guide the search for particular genes in genomes too large to be sequenced.

The picture below shows a segment of a typical genome map (in this case, from Dictyostelium). Each of the names on the map represents a unique marker of known sequence, whose position in the genome (the long horizontal line) has been mapped.