Only around a third of the world's remaining forest cover survives in the form of Intact Forest Landscapes (IFL), and that proportion is declining. Loss of intactness could impact on biodiversity in many ways but the relationship between intactness and extinction risk has not been quantified. We created Extent of Suitable Habitat (ESH) maps for all the world's forest‐dependent birds and intersected them with an independently derived IFL layer. We also estimate the proportion of the total global range‐rarity of forest‐dependent birds that is captured by IFL. The majority of forest‐dependent bird species are now confined largely or entirely to be degraded, disturbed, or fragmented (non‐IFL) forests. Furthermore, only 22.5% of global hotspots of range‐rarity for forest‐dependent birds are found within intact forests. We find a very strong positive relationship between the global extinction risk of forest‐dependent birds and the proportion of forest within their ESH that is no longer intact. This effect was independent of overall range size and phylogeny. There was also a tendency for extinction risk to be higher in species that lost more intactness in their forest ESHs between 2000 and 2016. Restoring intactness to forest landscapes will reduce global extinction risk in forest‐dependent birds.