Developments in the outer space arena post the erstwhile USSR launching the first manmade satellite Sputnik in space on 4 October 1957 have transformed the world significantly. In order to ensure the exploration and use of outer space for peaceful purposes, the Committee on the Peaceful Uses of Outer Space (COPUOS) was set up by the United Nations General Assembly in 1959. Subsequently, this committee led to the foundation of the “Treaty on Principles Governing the Activities of States in the Exploration and use of Outer Space, including the Moon and Other Celestial Bodies”. This treaty is commonly known as the Outer Space Treaty (OST). This treaty was opened for signature on January 27, 1967 as a binding legal instrument. On January 27, 2017, this treaty competes 50 years. Over the years this treaty has largely ensured responsible conduct of space activities. This book attempts to examine and contextualize the treaty and its relevance in the 21stcentury while tracing its journey over the last fifty years.