the Indonesian province of Papua is the western half of which island?

It is the island of NEW GUINEA.

The island is composed of two countries:

INDONESIA and PAPUA NEW GUINEA.

IRIAN JAYA (Indonesia) is the western half of the island.

PAPUA NEW GUINEA is the eastern half of the island.

The Island of New Guinea.

The eastern half of the island of New Guinea - second largest in the world - was divided between Germany (north) and the UK (south) in 1885. The latter area was transferred to Australia in 1902, which occupied the northern portion during World War I and continued to administer the combined areas until independence in 1975. A nine-year secessionist revolt on the island of Bougainville ended in 1997 after claiming some 20,000 lives.

Indonesia continues to face a low intensity separatist guerilla movement in Papua (a.k.a. Irian Jaya Barat).

the Indonesian province of Papua is on the western half of New Guinea island while the eastern half is the country of PAPUA NEW GUINEA.

Papua New Guinea

New Guinea

I believe it is New Guinea, hope this has helped!