Taeil, 31, whose legal name is Moon Tae-il, received the sentence last week along with two other co-defendants, after pleading guilty last month, as reported by The New York Times.
The co-defendants, surnamed Lee and Hong, were also sentenced to the same prison term.
The three men met the tourist at a bar in Seoul in June 2024. They then took her in a taxi to the home of one of the defendants, where they sexually assaulted her while she was heavily intoxicated, according to Korea Herald.
All three men have also been ordered to complete 40 hours of a sexual violence treatment program.
South Korean media reported that the presiding judge called the crime "very serious," noting that the men "took advantage of the victim being intoxicated and incapable of resistance" to commit the assault.
"The victim is a foreign tourist and she likely suffered significant psychological distress," the judge added.
Prosecutors had initially demanded a seven-year prison sentence for each of the men.
Taeil debuted in 2016 as part of a sub-unit of NCT, a popular boy band under SM Entertainment, one of South Korea's largest K-pop labels. His most recent solo work was a track for the historical drama "Missing Crown Prince," which aired last year.
In 2021, he set a Guinness World Record for being the fastest to reach one million followers on Instagram. His account, which had 4.3 million followers, is currently set to private, and videos from his YouTube channel have been removed.