Belgium has the particularity of being the only currently existing European monarchy that does not follow the tradition best described by the catchphrase "The king is dead, long live the king!". Instead, when the king dies, there is a gap, usually a couple of days, in which the government fulfils the royal duties. This lasts until the king's successor is sworn in before parliament. It is thus rather hard to determine the line of succession during that gap between the old and the new king. Should the next king be considered as no 1 in line of succession during that gap,  or should he already be considered as head of the family (but not as king) as soon as his predecessor dies? Therefore, I have opted to note both dates. Hence, when you see "10/17 Dec 1865", that means the previous king died December 10th, 1865 and his successor took the oath December 17th of that same year.

There is discussion wether or not the son born out of the marriage between King Leopold III of the Belgians and Princess Lilian of Belgium (called Princess of Retie) have rights to the throne. The orthodox theory is that he hasn't, but I belong to those who claim that he had, at least until his unapproved marriage in 1991. Therefore are have put him between brackets.

Some people interpret the Belgian constitution in a way that that King Albert II's sister Joséphine-Charlotte and her children have succession rights afther him and his descendants. However, I personally do not believe that this is what the people who wrote the constitution meant, and so, I have ignored that interpretation.

Belgium as three official languages: Dutch, French and German. Many members of the royal family have two names: a Dutch version and a French version. Therefore I will mention both names, starting with the Dutch one because the Dutch speaking part of the population is larger than the French speaking population. 

21 Jul 1831-24 Jul 1833

nobody

24 Jul 1833-26 May 1834

1. HRH Lodewijk-Filips/Louis-Philippe Prince of Saxe-Coburg and Gotha

26 May 1834-9 Apr 1835

nobody

9 Apr 1835-24 Mar 1837

1. HRH Leopold/Léopold Prince of Saxe-Coburg and Gotha

24 Mar 1837-12 Jun 1859

1. HRH Leopold/Léopold Prince of Saxe-Coburg and Gotha (since 16 Dec 1840 Duke of Brabant)
2. HRH Filips/Philippe Prince of Saxe-Coburg and Gotha (since 16 Dec 1840 Count of Flanders)

12 Jun 1859-10/17 Dec 1865

1. HRH Leopold/Léopold Duke of Brabant
2. HRH Leopold/Léopold Count of Hainault
3. HRH Filips/Philippe Count of Flanders 

10/17 Dec 1865-22 Jan 1869

1. HRH Leopold/Léopold Count of Hainault (since 17 Dec 1865 Duke of Brabant)
2. HRH Filips/Philippe Count of Flanders

22 Jan 1869-3 Jun 1869

1. HRH Filips/Philippe Count of Flanders

3 Jun 1869-8 Apr 1875

1. HRH Filips/Philippe Count of Flanders
2. HRH Boudewijn/Baudouin Prince of Saxe-Coburg and Gotha

8 Apr 1875-23 Jan 1891

1. HRH Filips/Philippe Count of Flanders
2. HRH Boudewijn/Baudouin Prince of Saxe-Coburg and Gotha
3. HRH Albert Prince of Saxe-Coburg and Gotha

23 Jan 1891-3 Nov 1901

1. HRH Filips/Philippe Count of Flanders
2. HRH Albert Prince of Saxe-Coburg and Gotha (since 14 Mar 1891 Prince of Belgium)

3 Nov 1901-3 Oct 1903

1. HRH Filips/Philippe Count of Flanders
2. HRH Albert Prince of Belgium
3. HRH Leopold/Léopold Prince of Belgium

3 Oct 1903-17 Nov 1905

1. HRH Filips/Philippe Count of Flanders
2. HRH Albert Prince of Belgium
3. HRH Leopold/Léopold Prince of Belgium
4. HRH Karel/Charles Prince of Belgium

17 Nov 1905-17/23 Dec 1909

1. HRH Albert Prince of Belgium
2. HRH Leopold/Léopold Prince of Belgium
3. HRH Karel/Charles Prince of Belgium 

17/23 Dec 1909-7 Sep 1930

1. HRH Leopold/Léopold Prince of Belgium (since 23 Dec 1909 Duke of Brabant)
2. HRH Karel/Charles Prince of Belgium (since 2 Feb 1910 Count of Flanders)

7 Sep 1930-17/23 Feb 1934

1. HRH Leopold/Léopold Duke of Brabant
2. HRH Boudewijn/Baudouin Prince of Belgium (since 10 Sep 1930 Count of Hainault)
3. HRH Karel/Charles Count of Flanders 

17/23 Feb 1934-6 Jun 1934

1. HRH Boudewijn/Baudouin Count of Hainault (since 23 Feb 1934 Duke of Brabant)
2. HRH Karel/Charles Count of Flanders

6 Jun 1934-18 Jul 1942

1. HRH Boudewijn/Baudouin Duke of Brabant
2. HRH Albert Prince of Belgium (since 7 Jun 1934 Prince of Liège)
3. HRH Karel/Charles Count of Flanders

18 Jul 1942-16/17 Jul 1951

1. HRH Boudewijn/Baudouin Duke of Brabant
2. HRH Albert Prince of Liège
(3. HRH Alexander/Alexandre Prince of Belgium)
3/4. HRH Karel/Charles Count of Flanders 

16/17 Jul 1951-15 Apr 1960

1. HRH Albert Prince of Liège
(2. HRH Alexander/Alexandre Prince of Belgium)
2/3. HRH Karel/Charles Count of Flanders

15 Apr 1960-19 Oct 1963

1. HRH Albert Prince of Liège
2. HRH Filip/Philippe Prince of Belgium
(3. HRH Alexander/Alexandre Prince of Belgium)
3/4. HRH Karel/Charles Count of Flanders

19 Oct 1963-1 Jun 1983

1. HRH Albert Prince of Liège
2. HRH Filip/Philippe Prince of Belgium
3. HRH Laurent Prince of Belgium
(4. HRH Alexander/Alexandre Prince of Belgium)
4/5. HRH Karel/Charles Count of Flanders

1 Jun 1983-14 Mar 1991

1. HRH Albert Prince of Liège
2. HRH Filip/Philippe Prince of Belgium
3. HRH Laurent Prince of Belgium
(4. HRH Alexander/Alexandre Prince of Belgium)

14 Mar 1991-10 Jul 1991

1. HRH Albert Prince of Liège
2. HRH Filip/Philippe Prince of Belgium
3. HRH Laurent Prince of Belgium

10 Jul 1991-9 Dec 1991

1. HRH Albert Prince of Liège
2. HRH Filip/Philippe Prince of Belgium
3. HRH Astrid Princess of Belgium, by marriage de jure Hereditary Princess of Modena
4. HI&RH Amedeo Prince of Belgium
5. HI&RH Maria Laura Princess of Belgium
6. HRH Laurent Prince of Belgium

9 Dec 1991-31 Jul/9 Aug 1993

1. HRH Albert Prince of Liège
2. HRH Filip/Philippe Prince of Belgium
3. HRH Astrid Princess of Belgium, by marriage (de jure Hereditary Princess of Modena)
4. HI&RH Amedeo Prince of Belgium
5. HI&RH Maria Laura Princess of Belgium
6. HI&RH Joachim Prince of Belgium
7. HRH Laurent Prince of Belgium 

31 Jul/9 Aug 1993-11 Oct 1995

1. HRH Filip/Philippe Prince of Belgium (since 9 Aug 1993 Duke of Brabant)
2. HRH Astrid Princess of Belgium, by marriage (de jure Hereditary Princess of Modena)
3. HI&RH Amedeo Prince of Belgium
4. HI&RH Maria Laura Princess of Belgium
5. HI&RH Joachim Prince of Belgium
6. HRH Laurent Prince of Belgium

11 Oct 1995-25 Oct 2001

1. HRH Filip/Philippe Duke of Brabant
2. HRH Astrid Princess of Belgium, by marriage de jure Hereditary Princess of Modena (since 7 Feb 1996: de jure Duchess of Modena)
3. HI&RH Amedeo Prince of Belgium (since 7 Feb 1996: de jure Hereditary Prince of Modena)
4. HI&RH Maria Laura Princess of Belgium
5. HI&RH Joachim Prince of Belgium
6. HI&RH Luisa-Maria Princess of Belgium
7. HRH Laurent Prince of Belgium

25 Oct 2001-23 Apr 2003

1. HRH Filip/Philippe Duke of Brabant
2. HRH Elisabeth Princess of Belgium
3. HRH Astrid Princess of Belgium, (by marriage de jure Duchess of Modena)
4. HI&RH Amedeo Prince of Belgium, (de jure Hereditary Prince of Modena)
5. HI&RH Maria Laura Princess of Belgium
6. HI&RH Joachim Prince of Belgium
7. HI&RH Luisa-Maria Princess of Belgium
8. HRH Laurent Prince of Belgium

23 Apr 2003-20 Aug 2003

1. HRH Filip/Philippe Duke of Brabant
2. HRH Elisabeth Princess of Belgium
3. HRH Astrid Princess of Belgium, (by marriage de jure Duchess of Modena)
4. HI&RH Amedeo Prince of Belgium, (de jure Hereditary Prince of Modena)
5. HI&RH Maria Laura Princess of Belgium
6. HI&RH Joachim Prince of Belgium
7. HI&RH Luisa-Maria Princess of Belgium
8. HI&RH Laetitia Maria Princess of Belgium
9. HRH Laurent Prince of Belgium

since 20 Aug 2003

01. HRH Filip/Philippe Duke of Brabant
02. HRH Elisabeth Princess of Belgium
03. HRH Gabriël/Gabriel Prince of Belgium
04. HRH Astrid Princess of Belgium, (by marriage de jure Duchess of Modena)
05. HI&RH Amedeo Prince of Belgium, (de jure Hereditary Prince of Modena)
06. HI&RH Maria Laura Princess of Belgium
07. HI&RH Joachim Prince of Belgium
08. HI&RH Luisa-Maria Princess of Belgium
09. HI&RH Laetitia Maria Princess of Belgium
10. HRH Laurent Prince of Belgium