The Dildo
The oldest one on record predates writing, agriculture, and the wheel by tens of thousands of years -- and no one gets to claim it.
In 2005, archaeologists working in a cave in Baden-Wurttemberg, southern Germany, pulled fourteen fragments of polished siltstone out of the ground. What emerged was a smoothed, deliberately shaped object roughly 20 centimeters long, carved from a material that doesn't occur naturally in that shape.
Radiocarbon dating placed it at roughly 28,000 to 30,000 years old, made by people living during the last Ice Age, long before agriculture, pottery, or permanent settlements existed. Archaeologists have since catalogued similar objects across cultures from ancient Greek vase paintings to Zanzibar, made from materials as varied as bronze and shaped bread.
There's no single culture, era, or continent that gets to claim this one. It appears to be one of the very few human inventions that arrived independently, repeatedly, and almost as early as humans arrived themselves.
There is no single inventor or origin culture for this object -- archaeological evidence places independently made versions across multiple ancient civilizations, predating recorded history by tens of thousands of years.