peer reviewed ; Interglacial to glacial transitions represent the most drastic turnovers in the Quaternary climate system. Yet, millennial-scaled climate variability and stochastic internal variability that result in these transitions remain still poorly understood. Here, three speleothem archives from two different cave systems in Belgium (Han-sur-Lesse and Remouchamps) are investigated using a multiproxy approach in order to characterize the last interglacial to glacial transition. The studied samples roughly span the period between 125 ka and 100 ka, covering a large part of the Eemian and early Weichselian. The speleothems show a high reproducibility for δ13C, which is interpreted as a proxy for past vegetation activity, controlled by vegetation assembly above the cave. All three speleothems show a drastic increase in δ13C between 118 to 117 ka, reflecting a rapid change of vegetation assembly from last interglacial temperate tree species towards glacial more open grass vegetation. This event shows a strong affinity in terms of timing and climatic expression with the Late Eemian Aridity Pulse (LEAP) at 118 ± 1 ka, identified in pollen records from Western Germany. Aligning the chronologies of the two independently dated Han-sur-Lesse speleothem records enables a more precise absolute chronology and provides an age of 117.7 ± 0.5 ka to the start of this event in the Belgian speleothems. This event marks a distinct transition in the Belgian speleothem proxies between Eemian optimum conditions and increased variability during the glacial inception and the start of this event at 117.7 ± 0.5 ka is therefore proposed as the Eemian- Weichselian transition and consequently the start of the glacial inception in the studied speleothems. High-resolution analysis shows that the 117.7 ± 0.5 ka event is initiated by a cooling pulse followed by a decrease in precipitation. A similar short-lived cooling event is also registered in multiple North-Atlantic sediment archives. This study hypothesizes that the origin of the ...