Bartek (Polish: Bartholomew) is an ancient oak tree in Poland. It grows in Zagnańsk near Kielce in the Świętokrzyskie Mountains. Its age, previously estimated at up to 1200 years, has recently been established to be 686 years (in 2016), with a corer used to extract a sample for a ring count. An accurate count is impossible, as Bartek's interior has hollowed with age. There are several older trees in Poland, both oaks and yews (some over 1000 years old), yet none of them has matched Bartek's fame.
The 33,5-metre<ref name=90drzew>Robert Tomusiak, Paweł Zarzyński. 90 drzew. Okazy niezwykłe. Centrum Informacyjne Lasów Państwowych. Warszawa. 2014. p.70.</ref> tall Bartek measures 970 cm at CBH (circumference at breast height) and 13.5 metres in girth at its base. Its crown spreads about 40 metres. King Casimir III (1310–1370) is known to have held court under Bartek. King Jan III Sobieski rested under the oak on his way back from the Battle of Vienna (1683). He reputedly hid a Turkish sabre, an arquebus and a bottle of wine inside it to commemorate the victory.