Not so rarely, we can hear discussions about if the Glasgow Rangers and Celtic should join the English Premier League. While that might shock you, many soccer teams play in another country's league system, and this top 10 will list the most successful of them. However, note that we've excluded teams that folded or are back playing in their native countries. Also, we won't count Canadian teams playing in the MLS, since Canada officially recognizes MLS as its highest domestic soccer league. Finally, the same goes for a bunch of foreign and satellite teams playing in Singapore, as they aren't allowed to represent the country in international club competitions.10. R&FR&F (Hong Kong) Soccer Limited won several titles in Hong KongR&F (Hong Kong) Soccer Limited is a soccer club from Guangzhou, mainland China that plays in Hong Kong. Even though Hong Kong has been a part of China since 1997, it retains its league system and international team. R&F is a satellite team of Guangzhou R&F, which is a member of the Chinese Super League.Although founded only in 2016, it's already one of the country's best clubs. In 2019, they finished second in the league, and they represent Hong Kong at the international level. The team has the ambition to dominate the local competitions, and thanks to its high budget, it probably will. The club plays its home games in Guangzhou but attracts less than 1000 fans on average.9. DPMM FCDPMM FC is by far the most successful soccer team from BruneiDuli Pengiran Muda Mahkota Football Club is a soccer club from Brunei, the only club on our list that played in three national championships! What they are also proud about is that most of DPMM FC players come from Brunei. After several seasons and a couple of titles in the local league, the team moved to Malaysia in 2005. They quickly earned a promotion to the top division, before reaching an excellent third place in their first season. However, after only two years, DPMM FC joined the Singapore Premier League and won the Singapore League Cup multiple times.Owned by the Prince of Brunei, who was a goalkeeper for the team, DPMM FC managed an incredible feature in 2019, since they won both Singapore and Brunei League. This is surprising for a nation with one of the worst international soccer teams.8. FC AndorraFC Andorra had several successful Copa del Rey runsFutbol Club Andorra is by far the biggest club in the tiny Principality of Andorra. It's also the only club from the country playing in the Spanish league system since 1948. For most of its existence, F.C. Andorra competed in Segunda Division B, a third level in the Spanish league system.Their biggest moment came in 1994 when they surprisingly beat Barcelona and Espanyol to win the Catalan cup. As for the official cup competitions, their best result came in 1995-96 when they were eliminated in Round 16 of Copa del Rey. Since being bought by famous Spanish soccer star Gerard Piqué, the club shows high ambitions and has a massive backing from sponsors. Don't be surprised if they reach the highest level of competition in Spain.7. The New Saints FCThe New Saints FC coat of arm represents local communities from Wales and England Based in England, The New Saints FC has been playing in the Welsh league system since 1959. As you can see on the coat of arms, the club represents two local communities – Oswestry in England and Llansantffraid-ym-Mechain in Wales.The New Saints earned its high place on our list as it won the Welsh league a record number of times. They've also represented Welsh football at the international level, including Champions League and UEFA Cup matches against Liverpool and Manchester City. However, they never managed to qualify for the first round of any UEFA competition.6. Derry City FCDerry City's crest contains traditional team colors - red, white and blackLocated in Northern Ireland, Derry City Football Club is surprisingly the only Northern Ireland soccer club regularly playing in the Republic of Ireland leagues since the mid-eighties. Ironically, they are also the only club to ever win the league, FAI Cup, and the League Cup in the same year (1989). Since then, they've added more trophies, which gave them a place in the European competitions.Also, Derry City became the first League of Ireland club to receive a premier UEFA license. Still, they've never been particularly successful at international competitions. They've only reached the first round of the UEFA Cup once in 2006 when they were beaten by Paris Saint Germain. But the most treasured possession of the club are its fans, as they've saved it from bankruptcy and now they own it. Derry City FC tickets are highly-sought items!5. Newport County AFCNewport County A.F.C. has two dates on its crest, as it was re-established in 1989Newport County A.F.C. is one of the four Welsh clubs playing in the English league system and apparently the worst of them. Still, the club is a regular member of the English Football League, which encompasses the top four divisions. The best days are far behind them, as their most significant result came in 1939 when they played in the Second Division (now Championship). However, that season was stopped thanks to Mr. Hitler and his ambitions to conquer the United Kingdom.The team recently had its 90 minutes of glory as they faced Manchester City in the 2018-19 edition of the F.A. Cup, and lost in the round of 16. The club also managed to win the Welsh Cup in 1980, while still playing in the English league system. This success allowed them to participate in the Cup Winner's Cup. There they reached the quarterfinals, barely losing to East German side Carl Zeiss Jena.4. Wrexham AFCDespite being the oldest club in Wales, Wrexham still lacks successWrexham AFC is the oldest club in Wales and one of the oldest clubs worldwide. They played at the top four English football levels for most of its existence, including several seasons in Division Two (now Championship). The club also had several notable F.A. Cup runs, reaching the quarterfinals on three occasions.However, they've also competed in Welsh Cup, winning it a record number of times. That was also their ticket to Europe, as they were regular in Cup Winners' Cup. In 1975-76 they barely lost in the quarterfinal to Anderlecht, which later won the competition. Eight years later, they dispatched mighty FC Porto in the first round. That's more than enough for position number four on our list. In 2021, a famous actor Ryan Reynolds bought the club, giving it a lot of publicity and hope for improvement.3. Cardiff City FCCardiff City is a member of the English league system for over a centuryCardiff City is one of the only two Welsh clubs to ever play in the top division of English football. They joined the English league system in 1920, and in 1924 the team already achieved their biggest success. They finished as the runners-up, with the same points total as the eventual winners Huddersfield Town. Since then, the club has mostly played in lower divisions.Cardiff City won a single domestic trophy in 1927, the FA Cup, thus becoming the first non-English club to do it. Recently, they were also the runners of the Football League Cup and also had players representing them at the World Cup. Cardiff City has also played more than ten European football seasons by winning multiple Welsh Cup trophies. They are the most successful Welsh club in Europe, reaching the semifinals of Cup Winners' Cup in 1968. The team also scored notable wins against Sporting Lisbon, Nantes, and even Real Madrid in the quarterfinals of Cup Winners' Cup in 1971.2. Swansea City AFCSwansea City AFC is the most successful Welsh club in the 21st centuryFounded in 1908, Welsh side Swansea already joined the English league system in 1921. Sixty years later, they finally managed to earn a promotion to the top level. Moreover, in 1982 they were even close to winning a title but eventually finished sixth, which is still their best performance. They are also a Welsh team with the most seasons spent in the Premier League and the only non-English club to win the Football League Cup (2013).Like other listed Welsh clubs, Swansea also managed to win tons of Welsh cups, thus securing a place in the European competitions. However, in 2013, Swansea also became the first Welsh club to qualify for Europe from the English league system. This was also their most successful European season, as they were defeated in the round of 32.1. AS Monaco FCAS Monaco is one of the most successful clubs in the French league historyAS Monaco was the obvious choice for the number one spot! Founded in 1924, the club immediately joined the French league system and is an integral part of it. AS Monaco FC is also the only club representing the nation that's not a UEFA or FIFA member. The club is still proud of its origins, as it plays home games in Monaco and is partially owned by the rulers of the country, House of Grimaldi.AS Monaco is also one of the most successful clubs in the French league, which is traditionally recognized as one of the world's five best. The club won the competition eight times and were the runners up on seven occasions. Moreover, they also have several cup titles and have played an important role in European competitions. Their most significant success came in 2004 when they were beaten in the UEFA Champions League's final. They were also runner-ups in the 1992 European Cup Winners' Cup final and have played Champions League semifinals on a few more occasions. Of course, they produced numerous world stars, including Kylian Mbappe.While many other clubs are not playing in their domestic leagues, these ten proved to be the most successful. They all deserve praise for their achievements, and some of them are even considered among the best clubs in the leagues they are playing in.Have we missed a team on our list? Which of these clubs is your favorite? Share your views with us a write a comment below.