Dildo
No single inventor can claim the dildo, which appears instead as a recurring human idea from Ice Age Europe to ancient Greece and Rome and far beyond.
The oldest solid candidate for a deliberately phallic sex aid is a polished siltstone object discovered in 2005 in Hohle Fels Cave in Baden-Württemberg, southern Germany, dated to around 28,000–30,000 years ago. Roughly 20 centimetres long and about 3 centimetres in diameter, it bears etched lines that resemble a glans, and its wear patterns suggest it saw both use in tool-making and very plausibly as a toy.
Later evidence from Greece, Rome and other regions shows leather and wooden forms, suggesting the idea spread widely long before the modern word 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.
The English word “dildo” appears much later, around the 1400s, while industrial materials such as rubber only arrive in the nineteenth century. We'll never be able to pinpoint its invention, just catalog a long chain of reinvention, with different cultures making the same basic object in their own materials and styles.
The dildo is less an invention with a single creator than a durable human solution that keeps resurfacing wherever bodies, curiosity and spare materials collide.