This study examines the stock market integration in cross-regional countries of developed, emerging, and frontier markets based on low correlation. The objective of the study is to identify the diversification opportunities and link between correlation and integration among country-level stocks. For this purpose, we select 62 countries from all three classifications of developed, emerging, and Frontier Markets. We constructed portfolios by selecting least 5 correlated countries denoted with Pjt in which each country has a correlation of less than .10 with base country Pit. Thirty-two countries fulfill the criteria of low correlation; 7, 13 and 12 from developed, emerging and frontier markets, respectively. Panel co-integration and VECM are applied to test the stock market integration and long & short-run linkages between country-level portfolios designed based on low correlation criteria. After conditioning for oil price movements, S&P 500 and exchange rate, we found Canada, France and Germany from developed category; Chile, Colombia, Greece, South Korea, Malaysia, Pakistan and Philippine from emerging category; and Bahrain, Jordan, Kuwait, Morocco, and Sri Lanka from frontier category have long-run diversification opportunities. Countries including; Canada and Italy from developed category; Argentina, Chile, China, Colombia, India, Indonesia, South Korea, Mexico and the Philippine from emerging category; and Bahrain, Kuwait, Morocco, Nigeria, and Tunisia from emerging category have short-run diversification opportunities.