Udayana's doctrine of God can be said to be the culmination of a process of development of about a millennium, a process marked by rational controversy with the opponents of theism, notably the Buddhists and the Mimamsakas, in which strict logical accuracy went hand in hand with greater precision of ideas and depth of thought. Due, in large measure, to the excessive and almost exclusive importance attached to the problems of epistemology, the successors of Udayana did not make-at least as far as the content is concerned -any substantial contribution to the doctrine of God. Udayana's rational or natural theology thus represents the acme of perfection attained by the Nyaya-Vaisesikas in their rational search for God. Moreover, we can say that in studying the doctrine of God as developed and perfected by Udayana we study the Indian rational or natural theology in general. The present work is a modest attempt to give a brief introduction to the doctrine of God as found in Udayana's works in general, in his Nyayakusumanjali in particular. The writer’s aim has been to give as faithful an interpretation of Udayana's ideas as possible in the given amount of space. How far he has succeeded in the realization of his aim should be left to the judgement of the critical reader.