What is the most oldest thing?

The oldest known objects in the universe are zircon crystals found in Australia, dating back about 4.4 billion years. In terms of living organisms, certain bristlecone pine trees may live for over 5,000 years, with some clonal colonies, like Pando, being thousands of years old. Additionally, the oldest known fossils are stromatolites, which are around 3.5 billion years old.