 Hello students, my name is Professor Urjit Yagnik, I am a professor at the physics department IIT Bombay. Welcome to this course on path integral and functional methods in quantum field theory. This course is primarily an advanced course. It is meant for PhD students who will go on to do a PhD in high energy physics or elementary particle physics. However, some parts of the course would be useful even for MSc students who have plans of proceeding to high energy physics and even for some BSE students who are just interested in understanding quantum mechanics more deeply. So, accordingly the first quarter of the course is a general introduction and a general discussion of quantum mechanics and in it we highlight the fundamentally multi particle nature of quantum mechanics. So, this would be of useful to students even of BSE, it will help it if they have a prior introduction to quantum mechanics, but if not this will be their first introduction. And here we also develop the path integral method due to Feynman which is a beautiful alternative way of thinking about quantum mechanics. Here also it is useful if you already know the Schrodinger and Heisenberg picture approach, but if not this will be your first introduction to formulation of quantum mechanics. So, this is about one quarter of the course. The next one quarter, we develop this path integral method into what we call a functional method where due to the many particle nature of relativistic quantum theory, it is necessary to introduce fields instead of particles. And so, we continue to use the path integral formulation, but not for trajectories but for fields. Here we develop some methods that will be primarily useful to students who will go on to doing theoretical particle physics, but here an MSc student may benefit by getting some advance ideas early. The second half of the course is then leading on to Yang-Mills theory. This is the most fundamental framework that describes all of elementary particle physics. It is one of the crowning achievements of 20th century, just as general theory of relativity is the correct relativistic theory of gravity, the Yang-Mills theory provides the framework to describe the strong as well as the electroweak forces and is of fundamental importance to all of particle physics. Thank you and welcome to the course.