The 39th century BC was a century which lasted from the year 3900 BC to 3801 BC.
Events
alt=Two wooden posts set in the ground and crossing at an angle support a wooden board, which disappears into tall green reeds|thumb|A replica of the Sweet Track
- The Post Track, an ancient causeway in the Somerset Levels, England, is built, c. 3838 BC. It is one of the oldest engineered roads discovered in Northern Europe.
- The Sweet Track, an ancient causeway also in the Somerset Levels, the oldest timber trackway discovered in Northern Europe, is built in 3807 BC or 3806 BC; tree-ring dating (dendrochronology) enabled very precise dating.
- Plough in use.