Papua is the largest province of Indonesia, comprising a majority part of the western half of the island of New Guinea and nearby islands (see also Western New Guinea). The province originally covered the entire western half of New Guinea, but in 2003, the western portion of the province, on the Bird's Head Peninsula, was declared by the Indonesian Government as a separate province named West Irian Jaya (now West Papua).
Within Indonesia and West Papua itself, 'Papua' usually refers to the entire western half of New Guinea - West Papua - despite its division into separate provinces by the Indonesian government. What is referred to as 'Papua' in Indonesia is generally referred to as 'West Papua' internationally - especially among networks of international solidarity with the West Papuan national movement.
"Papua" is the official Indonesian and internationally recognised name for the province. During the Dutch colonial era the region was known as part of "Dutch New Guinea" or "Netherlands New Guinea". Since its annexation in 1969, it became known as "West Irian" or "Irian Barat" until 1973, and thereafter renamed "Irian Jaya" (roughly translated, "Glorious Irian") by the Suharto administration. This was the official name until "Papua" was adopted in 2002. Today, natives of this province prefer to call themselves Papuans rather than Irianese. This may be due to etymology (variously identified as a real etymology or a folk etymology) of the name Irian which stems from the acronym Ikut Republik Indonesia, Anti Nederland (join/follow the Republic of Indonesia, rejecting the Netherlands).
The name "West Papua" was adopted in 1961 by the New Guinea Council until the United Nations Temporary Executive Authority (UNTEA) transferred administration to the Republic of Indonesia in 1963. "West Papua" has since been used among Papuan separatists and usually refers to the whole of the Indonesian portion of New Guinea. The other Indonesian province that shares New Guinea, West Irian Jaya, has been officially renamed as "West Papua".
Source : http://en.wikipedia.org/wiki/Papua_%28province%29