The occurrence of the tropical seagrass Halophila stipulacea (Hydrocharitaceae) is recorded for the first time on the Caribbean coast of Martinique (French West Indies, Caribbean Sea). Specimens were observed, since a large survey in 2006, on sandy substrates between 3 m and 32 m depths in this area. The species was found in mono-specific patches or mixed with other macrophytes as Syringodium filiforme (seagrass) and/or Ulva intestinalis (green alga). Halophila stipulacea was previously identified on the coasts of Dominica and St Lucia, two islands nearby our study area. While its presence was presumed to be in Martinique, it was never officially recorded. These findings off the coast of Martinique further define the distribution and widespread occurrence of this alien species within the Caribbean Sea.