This dataset comprises multibeam bathymetry and very high resolution seismic data acquired over the Lansdowne Bank (New Caledonia, SW Pacific), during the SEDLAB cruise. The latter was a 29 day research cruise on the French national fleet ship R/V ALIS that took place in April and May 2018. The main aim was to characterise the sedimentary dynamics and the stratigraphic architecture of the Lansdowne Bank, a partly drowned, isolated rimmed carbonate platform of around 4000 km2 located offshore New Caledonia in the SW Pacific. More than 2000 km2 of new multibeam data, 7 single-channel SPARKER seismic profiles, along with 15 rock dredges and 8 sediment gravity cores were acquired on the bank top and adjacent slopes. These data reveal that the bank is typified by an almost continuous 4 km wide reef rim located in ca. 50 m water depth, showing typical “spurs and grooves” patterns. This outer rim surrounds a paleolagoon that gently deepens towards the inner platform, reaching up to 100 m water depth. Pinnacle reefs, up to 20 m high, are common close to the external reef rim, but are also scattered within the inner platform. Surprisingly, no obvious transfer axes across the reef rims, internal channels, tidal shoals or any clear current-related bedforms were imaged on the bank top. The bank is bordered by very steep slopes showing numerous bypass features such as canyons, channels and gullies. Additionally, spectacular bank margin collapses were identified. They are evidenced by up to 10 km wide intraslope and bank edge failure scarps, resulting in a scalloped geometry of the bank margin. Scarps are associated with km-sized blocks at the base-of-slope. Integration of all surface and subsurface data, together with post-cruise sedimentological, biostratigraphic and radiometric analyses on rock and sediment samples will hopefully bring new insight into the onset, aggradation and drowning history of the platform in relation to past sea-level changes and vertical tectonic movements. We believe that such results are relevant for the understanding of carbonate slope processes as well as platform-to-basin sediment budgets.