how many illegal aliens are in the united states

The best current estimate depends on the definition you use, but a widely cited 2025 estimate is about 18.6 million unauthorized immigrants in the United States. Another mainstream news estimate referenced in 2025 says “over 10 million” undocumented immigrants, showing that counts can vary a lot by method and source.

Why the number varies

Different groups use different data sources and assumptions, so the total can shift significantly. Some estimates try to infer the size of the unauthorized population from Census-based data, while others report narrower operational counts or older baselines.

Context

For comparison, one 2026 health-policy summary said there were about 50 million immigrants living in the U.S. in 2024, including 24 million noncitizen immigrants and 26 million naturalized citizens. That broader immigrant total is not the same as the unauthorized population, but it helps show the scale of the overall foreign-born population.

Practical takeaway

If you want a single headline number, 18.6 million is a current high-end estimate from FAIR in 2025. If you want the most neutral phrasing, say “roughly 10 million to 19 million, depending on the source and methodology”.

TL;DR: The most recent widely reported estimate I found is about 18.6 million unauthorized immigrants in the U.S., but credible sources differ substantially on the exact figure.