Principle purpose of this lecture is to presentation on Regional Economic Integration. Here briefly explain on levels of economic integration among nations, Economic and political arguments for/against. Here also discuss on History/scope, scope and future prospects for: EU, NAFTA, MERCOSUR and APEC. Generally Regional Economic Integration agreements among geographically proximate countries to reduce/remove tariff and non-tariff barriers to free flow of: Goods, Services and Factors of production.