Some state leaders in the world have held onto their positions for decades. States where head of state differs from head of government are mainly parliamentary systems. Often a leader holds both positions in presidential systems or dictatorships. Some states have semi-presidential systems where the head of government role is fulfilled by both the listed head of government and the head of state.
The list below is of current state leaders ordered by their continuous tenure in a position of national leadership. In countries with different heads of state and heads of government, both offices are listed. For leaders who held the same office prior to their state’s independence, the start of their tenure is used, not independence. Acting presidents are included in this list, but if a leader has non-consecutive terms, only the current period of service is listed.
Here are the top 20 longest serving state leaders in the world.
| Rank | Name | Position | Assumed office |
| 1. | Hassanal Bolkiah | Sultan and Prime Minister of Brunei | October 4, 1967 |
| 2. | Margrethe II | Queen of Denmark | January 14, 1972 |
| 3. | Carl XVI Gustaf | King of Sweden | September 15, 1973 |
| 4. | Paul Biya | President of Cameroon | June 30, 1975 |
| 5. | Teodoro Obiang Nguema Mbasongo | President of Equatorial Guinea | August 3, 1979 |
| 6. | Ali Khamenei | Supreme Leader of Iran | October 13, 1981 |
| 7. | Hans-Adam II | Prince Regnant of Liechtenstein | August 26, 1984 |
| 8. | Hun Sen | Second Prime Minister of Cambodia | December 26, 1984 |
| 9. | Yoweri Museveni | President of Uganda | January 29, 1986 |
| 10. | Mswati III | King of Eswatini | April 25, 1986 |
| 11. | Harald V | King of Norway | June 1, 1990 |
| 12. | Isaias Afwerki | President of Eritrea | April 27, 1991 |
| 13. | Emomali Rahmon | President of Tajikistan | November 19, 1992 |
| 14. | Alexander Lukashenko | President of Belarus | July 20, 1994 |
| 15. | Letsie III | King of Lesotho | February 7, 1996 |
| 16. | Denis Sassou Nguesso | President of the Congo | October 25, 1997 |
| 17. | Henri | Grand Duke of Luxembourg | March 3, 1998 |
| 18. | Abdullah II | King of Jordan | February 7, 1999 |
| 19. | Hamad bin Isa Al Khalifa | King of Bahrain | March 6, 1999 |
| 20. | Mohammed VI | King of Morocco | July 23, 1999 |
