WO or Wo may refer to:
World War II (often abbreviated to WWII or WW2), also known as the Second World War, was a global war that lasted from 1939 to 1945. The vast majority of the world's countries—including all the great powers—eventually formed two opposing military alliances: the Allies and the Axis.
World War I (often abbreviated as WWI or WW1), also known as the First World War or the Great War, was a global war originating in Europe that lasted from 28 July 1914 to 11 November 1918. Contemporaneously described as "the war to end all wars", it led to the mobilisation of more than 70 million military personnel, including 60 million Europeans, making it one of the largest wars in history.
WorldCat is a union catalog that itemizes the collections of 72,000 libraries in 170 countries and territories that participate in the Online Computer Library Center (OCLC) global cooperative.
The wolf (Canis lupus), also known as the gray/grey wolf, timber wolf, or tundra wolf, is a canine native to the wilderness and remote areas of Eurasia and North America.
The World Health Organization (WHO) is a specialized agency of the United Nations that is concerned with international public health.