This paper presents a global model‐based country‐scale quantification of urban N and P mass flows from humans, animals, and industries and their waste N and P discharges to surface water and urban waste recycling in agriculture. Agricultural recycling was practiced commonly in early twentieth century Europe, Asia, and North America. During the twentieth century, global urban discharge to surface water increased ~3.5‐fold to 7.7 Tg yr‐1 for N and ~4.5‐fold to 1.0 Tg yr‐1 for P; the major part of this increase occurred between 1950 and 2000. Between 1900 and ~1940, industrial N and P flows dominated global surface water N and P loadings from urban areas; since ~1940, human wastes are the major source of urban nutrient discharge to both surface water and agricultural recycling. During the period 1900–2000, total global recycling of urban nutrients in agriculture increased from 0.4 to 0.6 Tg N yr‐1 and from 0.07 to 0.08 Tg P yr‐1. A large number of factors (the major ones related to food consumption, urban population, sewer connection, and industrial emissions) contribute to the uncertainty of −18% to +42% for N and −21% to +45% for P around the calculated surface water loading estimate for 2000. Key Points A global model was made to inventory urban 20th century nutrient flows Global surface water discharge increased ~3.5‐fold for N and ~4.5‐fold for P At present human excreta and detergents are the major urban nutrient sources