(Most of this is a reposting from November.)
The oldest regimes in the world are in the middle east.
Al Sabah, Kuwait – since 1752
Al Khalifa, Bahrain – since 1783
Al Thani, Qatar – since 1825
Al Nahyan, Abu Dhabi – since 1761
Al Maktoum, Dubai – since 1833
Al Qasimi, Sharjah – since 1727
Al Nuaimi, Ajman – since c 1780
Al Mu‘alla, Umm al-Qaiwain – since 1775
Al Qasimi, Ras al-Khaimah – since c 1725
Al Sharqi, Fujairah – since 1876
Al Said, Oman – since 1749
Kuwait and Bahrain are, to a degree, constitutional monarchies. They have parliaments. The Kuwaiti parliamentary system was set up in 1962, I believe to absorb heightened political feelings in the age of Nasser and in fear of pan-Arabism. The British had withdrawn their “protection” from Kuwait in 1961, a decade before they withdrew it from Bahrain, Qatar, the Trucial States (now UAE) and Oman. The Bahraini parliamentary system was set up in 2002.
The same years that saw the arrival of the Gulf monarchies saw the establishment of the Durrani Empire in Afghanistan (1747) and Qajar dynasty in Persia (1794).
The present Swazi monarchy was established in 1745.
The Alaouites came to power in Morocco in 1666 and still rule, in theory constitutionally. The Chakri dynasty came to power in Thailand in 1782, but this is a constitutional monarchy.
Old post: Qatar.