Most Difficult Languages for English Speakers

Difficulty source: The US Dept. of State's School of Language Studies. https://www.state.gov/foreign-language-training/

Native speaker population source: Each language's Wikipedia page

Category III and Category IV are the highest difficulty tiers School of Language Studies ranking.

Note: Per the difficulty source, this list is non-exhaustive. Languages that aren't consistently taught at the School of Language Studies are not included. Only languages with more than 10 million native speakers are included.