Abstract: In this study, a novel objective image quality metric is proposed. The proposed metric can be used for image fusion evaluation without a reference image. The proposed metric is an extension of Mutual Information (MI) metric based on Renyi entropy which is a single parameter generalization of Shannon entropy. Renyi MI measures the total amount of information that fused image contains about source images. Also, the overlapping information problem is considered by using Generalized Normalized MI to avoid its influence. Experimental results show that the presented metric well correlated with human subjective evaluations and it is much better than conventional MI metrics based on Shannon entropy and Tsallis entropy.