Around the world, coastal urbanization continues to replace natural marine habitats with engineered structures, resulting in wholesale changes to shallow-water ecosystems and associated socioecological impacts. This process is expected to continue over the coming decades. The development of meaningful strategies to minimize future impacts requires an understanding of the rate at which ‘coastal hardening’ will take place regionally. Here we show that coastal infrastructure has replaced more than half (52.9 ± 4.9%) of the coastline associated with 30 global urban centres. The regional extent of coastal hardening is explained by eight predictor variables associated with shipping, boating, regional economies, populations and coastline length. Using a case study approach, we forecasted a 50–76% expansion of coastal infrastructure over a 25-year period. Our model can aid decision-makers to anticipate increases in coastal hardening, supporting identification and management of future threats to coastal ecosystems alongside social, economic and cultural objectives.