COUNTY · VA
Loudoun County, Virginia
Loudoun County is a county in Virginia with FIPS code 51107 and an estimated population of 436,347 (Census 2023), 4th largest of 133 in the state.
County facts
- Name
- Loudoun County
- State
- Virginia
- Type
- county
- FIPS code
- 51107
- State FIPS
- 51
- Population (2023)
- 436,347
- Change since 2020
- +3.2%
- State rank
- 4 of 133
Population is the Census Bureau’s Vintage 2023 estimate.
Questions
What is the FIPS code for Loudoun County?
Loudoun County, Virginia has the five-digit FIPS code 51107: 51 for the state and 107 for the county.
What state is Loudoun County in?
Loudoun County is in Virginia.
How do I know if an address is in this county?
Use the address lookup. ZIP codes and city names can cross county lines, so an address is the reliable check.
Sources: U.S. Census Bureau geographic reference files; Census Bureau Population Estimates, Vintage 2023. Last reviewed 2026-10-27.