The Gulf of Bothnia is a shallow, elongate basin dividing Sweden and Finland, and is located in the centre of the terrain formerly occupied by the Fennoscandian Ice Sheet (FIS). It is considered to have hosted a variety of different glaci-dynamic environments during the evolution of the FIS, but direct glacial geological or geomorphological evidence from the Gulf itself is almost entirely lacking. Recent acquisition of high-resolution multibeam data enables direct investigation of the basin for the first time. These data reveal a wealth of glacial landforms in the Gulf of Bothnia including glacial lineations, ribbed moraine, eskers, meltwater channels, moraines, crevasse-squeeze ridges and iceberg ploughmarks with a variety of different morphologies. Distinct landform assemblages record multiple ice-flow events or phases of differing glaci-dynamic character. Two contrasting glacial landform assemblages are presented from the western and northern Bothnian Sea. Assemblage 1, located in the western Bothnian Sea (Fig. 1), comprises an 80 km long field of approximately 950 pronounced, elongate and aligned mounds (Jakobsson et al. 2016). These mounds have a typical length of about 900 m, width of c. 300 m and amplitude of c. 6 m, and are formed in glacial till, often clustered locally with multiple individuals formed in/of a single till patch. Many mounds appear to be bedrock-cored, however, with preferential till accumulation over bedrock obstacles (Fig. 1e). Within this population, the mounds show progressive downstream elongation. Overall, they possess a SSE orientation, with some slight southward shift in the downstream and western parts of the assemblage. The SSE-orientated features are cross-cut and terminated at their downstream end by a SW-orientated group of much narrower (<50 m), lower-amplitude ( c. 1–4 m) and elongate lineations (Fig. 1h). A well-developed channelized landform system weaves southward through the streamlined mounds (Fig. 1f), comprising both incised channel …