On behalf of the Organising Committee and ACUUS, it is our pleasure to invite you to Singapore in 2023 for the 18th Conference of the Associated Research Centers for the Urban Underground Space (ACUUS 2023 Singapore). ACUUS 2023 combines with the 2nd International Conference on the Exploration and Utilisation of Underground Space (EUUS-2). The EUUS conference series is an ACUUS initiative with a focus on urban geology and underground resources.