The study of the lower Garonne between 170 and 200 km upstream of its current mouth reveals a complex evolution of the valley during the Last Glacial and the Holocene. The architecture and chronology of Late Pleistocene to Holocene alluvial deposits in the lower Garonne have been studied in details based on data (boreholes, trenches, ground-penetrating radar, numerical dating) collected in quarries and during archaeological surveys (Bertran et al., Geomorphology, in press). The ages were obtained from sand beds (OSL) and plant debris (14C) from clay and peat at the base of abandoned channel fills. The preserved alluvial bodies, dated between ca. 38 ka and present, show that the river retained a meandering or anabranching pattern throughout this period, associated with the formation of lateral accretion packages and scroll bars in the convexity of meanders. A narrow incision was identified along the Garonne Valley within the deepest alluvial deposits, and linked with an ’incised valley’ described in the estuary. This valley incision occurred between ca. 26 and 18 ka and therefore can be interpreted to be in connection to the LGM low sea level. It reached up to 19 m in the study area, and occurred while the riverbed adjusted in response to the base level drop. The upstream propagation of the knickpoint to the study area probably required a delay of several millennia. The rapid sea level rise during deglaciation would then have caused the canyon to fill in, followed by the re-establishment of a ”normal” river regime from 18 ka onwards when a new equilibrium was reached. Since ca. 18 ka, the lateral migration of meanders widened the plain without any significant incision of the Oligocene marl bedrock. The Early-Middle Holocene was characterized by the development of highly sinuous meanders, while sinuosity decreased in a late phase including the Little Ice Age. The morphology of the Garonne floodplain during the Last Glacial remains difficult to assess in detail. While the presence of large lateral accretion packages in a sector dated ca. 18 ka attests to a meandering or anabranching pattern, no MIS 2 abandoned channel has been observed in cross-section in the study area. One channel, with its large radius of curvature, was active during the Lateglacial (early MIS 1) and was abandoned during the Alleröd. Gravel beds on the MIS 2 and early MIS 1 point bars (MB3) at a higher elevation than on the Holocene MB2 suggests that flood discharges were higher during the earlier phase of floodplain evolution. Comparison with other lowland European rivers shows that the persistence of a meandering or anabranching pattern during MIS 2 is not an isolated case. The documented examples are associated with rivers typified by low valley slope, or situated in southern regions unaffected by permafrost and characterized by dense vegetation. The latter conditions would not have led to a drastic change in river discharge and bedload transport during the Last Glacial, as was the case for more northerly rivers where braiding seems to have been common.