| Honorific Prefix: | His Excellency |
| Adnan Mohd Ja'afar | |
| Office: | Ambassador of Brunei to Belgium |
| Term Start: | 20 April 2022 |
| Predecessor: | Abu Sufian Ali |
| Office1: | Ambassador of Brunei to East Timor |
| Term Start1: | 28 February 2019 |
| Term End1: | 16 November 2020 |
| Predecessor1: | Norazlianah Ibrahim |
| Successor1: | Wan Hadfi Lutfan |
| Office2: | High Commissioner of Brunei to Australia |
| Term Start2: | 2008 |
| Term End2: | 2008 |
| Predecessor2: | Jocklin Kongpaw |
| Successor2: | Sharip Othman |
| Birth Place: | Brunei |
| Occupation: | Diplomat |
Adnan bin Haji Mohd Ja'afar is a diplomat from Brunei who is the incumbent ambassador to Belgium since 2022, East Timor from 2019 to 2020, and high commissioner to Australia in 2008. Additionally, he is also representative to the Organisation for the Prohibition of Chemical Weapons (OPCW) since 2022.[1]
On 29 October 2008, Sultan Hassanal Bolkiah handed over Adnan's letter of credentials, amid his appointment as the new high commissioner to Australia. He previously served as Director of the Department of International Organizations at the Ministry of Foreign Affairs and Trade and as Deputy Permanent Representative at Brunei Darussalam's Permanent Mission to the United Nations in New York.[2]
After being appointed as the new ambassador to East Timor, on 15 January 2019, Adnan again received his letter of credentials at the Istana Nurul Iman.[3] Adaljiza Magno's remarks at the farewell reception on 16 November 2020 noted that Ambassador Adnan has strongly advocated for Timor-Leste's ASEAN membership since its inception.[4]
On 8 March 2021, Sultan Hassanal Bolkiah handed over Adnan's letter of credentials,[5] [6] which would officially be handed over to King Willem-Alexander on 20 April 2022.[7] On the same day, he handed over his credentials to the OPCW. As the non-resident ambassador to Luxembourg, he presented his credentials to Grand Duke Henri on 16 March 2022.[8] At the same time, he was the non-resident ambassador to Hungary.[9]
Dayangku Salina Binti Pengiran Haji Alli is Adnan's wife.[10]