We describe the publicly available CERDI-seadistance database, which contains bilateral maritime distances between 227 countries and territories. The relevant port(s) for countries with access to the sea is defined as the coastal cell of a country that contains the highest number of shipping lines, and each landlocked country is associated to the (foreign) port with the shortest road distance to its capital city. The length of the existing shortest sea route between the two ports is then computed; this represents the bilateral maritime distance included in our database, which also contains a few additional ancillary variables.