This dataset accompanies the publication "Non-indigenous seaweeds in the Northeast Atlantic Ocean, the Mediterranean Sea and Macaronesia: a critical synthesis of diversity, spatial and temporal patterns" (van der Loos, Bafort, Bosch, et al. 2023). The dataset is a compilation of non-indigenous marine seaweed species records from three main regions, namely the Northeast Atlantic Ocean (excluding Greenland), the Mediterranean Sea and Macaronesia. A total of 19,724 records of non-indigenous seaweed records were collected dating from 1808 to 2022. For each record, this dataset contains the following information: SPECIES_SCIENTIFIC_NAME: Currently accepted scientific species name of the record (as of April 2023) ORIGINAL_RECORD_SCIENTIFIC_NAME: Scientific name that was originally used in the record YEAR: Year in which the specimen was recorded. Where possible, this date refers to the year the species was first observed rather than when the record was published. In the absence of such information the date refers to the year the first record was published. LATITUDE: Latitude LONGITUDE: Longitude AREA: Northeast Atlantic Ocean, Macaronesia, or the Mediterranean Sea COUNTRY: Country where the specimen was recorded LOCATION: Location where the specimen was recorded LIFE_STAGE: For some records the life stage (gametophyte, sporophyte, tetrasporophyte) has been recorded DRIFT: Records reported as drifting material are noted in this column as "drift" DATA_SOURCE: The data source (e.g., publication, project data, herbarium specimen, personal data) REFERENCE: The reference