By 2050, 68% of people are projected to live in urban areas. As cities grow into steeper terrain, residents are increasingly exposed to hazards like rainfall-triggered landslides. However, despite thousands of yearly fatalities, few cities have established early warning systems to reduce weather-related landslide risk. Rainfall thresholds that identify landslide triggering conditions are a key component of early warning systems, but limited landslide inventory data has hindered efforts to determine thresholds for many cities. Furthermore, the magnitude and variability of thresholds in and between urban areas worldwide has yet to be quantified, leaving cities without inventories few options to learn from others. We compiled 1216 urban landslides to estimate rainfall intensity-duration thresholds for 26 cities worldwide and a global threshold for urban landslides with a multi-level regression model. We find that landslides were triggered under surprisingly similar rainfall conditions in most cities despite widely varying climates, topographies, and income classes. In 77% of cities, the median threshold is indistinguishable from the global average. We show that urban landslides occurred at lower threshold intensities than previously reported for multiple land-use types, while 31% of landslides were triggered below annual rainfall maxima. Our results suggest that anthropogenic hillslope modification and malfunctioning infrastructure facilitate slope failures in cities. We argue that urbanization harmonizes rainfall thresholds between cities, overprinting natural variability, and offer a baseline for warning in cities with sparse landslide records.