In this paper, a new image encryption algorithm has been introduced. The algorithm includes the Lorenz system in order to produce a chaotic data and uses it to mask the images for the secure encryption. Both the high sensitivity to the initial conditions and unpredictability have increased the capability of encrypting the images. The algorithm has been tested by different methods in order to evaluate the performance by various analyses such as the secret key size and sensitivity, histogram, correlation, differential (plain image sensitivity), information entropy analysis. The experimental results prove that the proposed encryption approach provides an efficient and secure approach for the image encryption.