It is difficult to accurately determine the ages of many trees, and there may be older trees out there that have not yet been discovered or accurately dated. However, here is a list of some of the oldest trees that have been reliably dated.
Age: 9550 years old
Located at: Fulufjället Mountain of Dalarna province in Sweden.
Age: 7200 years old
Located at: Yakushima in Japan
Age: 5000 years old
Located at: White Mountains of California
Age: 4800 years old
Located at: Wheeler Peak in eastern Nevada, United States
Age: 4000 years old
Located at: village of Llangernyw, Conwy, North Wales
Age: 4000 years old
Located at: Abarkuh in Yazd Province of Iran
Age: 3500 years old
Located at: Big Tree Park, Longwood, Florida
Age: 3200 years old
Located at: California
Age: estimated 2500 years old
Located at: Sequoia National Park, California
Age: estimated 2000 years old
Located at: Botswana