Barrio of Monacillo
Location of Monacillo shown in yellow.
Country	United States
Territory	Puerto Rico
Municipality	San Juan
Area
- Total	1.15 sq mi (2.98 km2)
- Land	1.15 sq mi (2.98 km2)
- Water	0.00 sq mi (0.00 km2)
Population (2000)
- Total	12,425
- Density	10,768.3/sq mi (4,157.66/km2)
	2000 census

Monacillo is a barrio in San Juan, Puerto Rico. It originally included the area that now forms the Barrio of Monacillo Urbano. In 2000 it had a population of 12,425 living in a land area of 1.15 square miles (2.98 km²). Monacillo is surrounded by Monacillo Urbano Barrio to the North, Cupey Barrio to the East, Caimito Barrio to the South, and the municipality of Guaynabo to the West.