The Arc of Instability is a proposed, interconnected chain of politically unstable nation states in the Asia-Pacific region. The term came into vogue in the late 1990s, proving especially popular with Australian politicians and journalists. The Arc is also sometimes to referred to as balkanisation in a modern, Asia-Pacific context. 
The term is used to suggest that the members of the Arc are interconnected to the point that destabilisation within one country can have major political, military and economic repercussions in neighbouring countries. For example, Australian media and politicians claimed the destabilisation of the Solomon Islands was the result of a copycat or domino effect of the 2000 Fijian coup d'état.
We cannot afford to have failing states in our region. The so-called 'arc of instability', which basically goes from East Timor through to the south-west Pacific states, means that not only does Australia have a responsibility in preventing and indeed assisting with humanitarian and disaster relief, but also that we cannot allow any of these countries to become havens for transnational crime, nor indeed havens for terrorism.
There is no official list of member states in the Arc, however it has traditionally been accepted to include South-East Asian and Oceanic nations such as Papua New Guinea, The Solomon Islands, East Timor, Indonesia and Fiji.
This is a partial list of some events within the Arc which have typically been seen as contributing to the region's instability: