The English Proficiency Index (EPI) from global language training company Education First (EF) ranked Sweden top out of 88 countries which don't have English as a national language.
The country overtook last year's winner, the Netherlands, which was relegated to second place. Singapore completed the top three, followed by Norway and Denmark.
Sweden has never been ranked outside the top five in the eight years the survey has been published, and has previously held the number one spot in 2012, 2013, and 2015.
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English proficiency was very high across the entire country, although highest in Stockholm, with Småland, Gotland and Öland performing slightly worse. Women had better English language knowledge than men in all of Sweden's geographical regions, a trend also seen in most of the countries surveyed.
'Very high' proficiency was defined by EF as the ability to carry out complex, nuanced tasks in English, such as negotiating a contract with a native English-speaker, reading advanced texts with ease, and using nuanced and appropriate language in social situations.
Pia Sundqvist, a lecturer in English at Karlstad University, told the TT newswire that contributing factors towards Swedes' success in the language were subtitled media and a high standard of language teaching.
The report is based on a comparison of English skills measured by testing 1.3 million people, who voluntarily applied to take the test, in 88 countries. In Sweden a total of 3,600 people took part.
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English has become the working language in many Swedish companies. Photo: AP Photo/Alastair Grant