The currently longest reigning dynasty (in other words still reigning as of today):

1. Japan: Imperial House of Japan, 660 BC - present (founder: Jimmu)

Note Wikipedia: There is no historical evidence for the genealogical relationships, and in most cases even the existence of the first 25 emperors.

2. Netherlands: House of Orange-Nassau, 1544 - present (founder: William of Orange Nassau)

3. Spain: House of Bourbon, 1555 - present

Some other old ones:

4. Liechtenstein: House of Liechtenstein, 1608 - present

5. Bahrain: House of Al Khalifa, 1766 - present

6. Thailand: Chakri Dynasty, 1782 - present

7. UK: House of Windsor, 1865 - present

previous answer: Our bulgarian dinasty , Dulo.

Dulo Dynasty (2137 BC - 753 AD)

The dynasty that ruled the longest in history is the Dulo Clan or the House of Dulo of Bulgaria. It ruled for 2,890 years. The Dulo Clan or the House of Dulo was the name of the ruling dynasty of the early Bulgars. It was the clan of Kubrat, founder of the Onogur state of Bulgars and Avars, also known as the Old Great Bulgaria. His sons later founded Danube Bulgaria.