Logic is very important subject and it is impossible to deny its role in the development of modern technology. In modern scenarios, sound decision making is just an impossible task without logic and critical thinking. This book is based on the handouts which I had prepared while teaching a course 'An Introduction to Logic' in a university class. The handouts were prepared after consulting different books on the topic. The list of the books which were consulted during the preparation of handouts is given at the end of this book. This book contains eight chapters. In first chapter, all introductory concepts required to learn logic are included. In second chapter the discussion is about the concepts of validity, soundness, strength and cogency of arguments. Third chapter would introduce critical think process. Fourth chapter would deal with the fallacies in arguments or fallacies which one would face during critical thinking process. Fifth and sixth chapters would deal with categorical propositions and syllogism respectively. Seventh chapter would elaborate the details of decision making process and in last chapter one would find the details about problem identification and problem solving skills.