Citizens from these seven are only able to visit just 185 countries without extra documentation.
South Korea edged up the ranking from October's index to join Singapore, offering access to 189 jurisdictions, thanks to a new visa-on-arrival agreement with India.
The UK and the U.S. continue to lose ground in the ranking, now occupying the 6th place (185 countries).
Notable movers in the latest ranking include South Korea, which reached a new high in second spot, while the U.S. and United Kingdom jointly share sixth spot - a significant fall from grace, given they jointly held the top spot in 2015. The number of countries that a specific passport can access becomes its visa-free "score". The island nation doesn't share the top spot with any other countries.
The Index ranks all the world's passports according to the number of destinations their holders can access without a prior visa. The Japanese passport allows visa-on-arrival travel to 190 destinations.
The Henley Passport Index also singled out several countries that have shot up the rankings in recent years.
Denmark, Finland, Italy, and Sweden now hold joint fourth place, while Spain and Luxembourg are in 5th.
Malta sits in 9 spot, with access to 182 destinations and St. Kitts and Nevis and Antigua and Barbuda hold 27 and 28 spot respectively, while Moldova remains in a strong position at 46 place, with citizens able to access 122 countries.
The United Arab Emirates (UAE) was one of the biggest climbers on the 2018 Henley Passport Index.
Dr. Christian H. Kälin, Group Chairman of Henley & Partners, said, "Historical data from the Henley Passport Index over the past 14 years shows an overwhelming global tendency towards visa-openness".
According to the index, the passport that provides holders the least access is the Iraqi passport, which provides visa-free travel to just 30 nations.
The Henley Passport Index is the only passport index that is based on International Air Transport Association data, enhanced by extensive in-house research, supported by expert commentary, and updated regularly throughout the year, making it the most robust, credible, and reliable index of its kind.
Henley and Partners, in particular, pointed to South Korea's progress over the years, . lauding its "proactive foreign affairs approach" and an "attitude that significantly benefits their citizens as well as the global community".