A Textbook on Fortran/2003 is designed for the beginners who have not been exposed to the earlier versions of the language. At the same time, those who have used earlier versions can look into it for new features. Whenever possible a complete Fortran program has been used to illustrate a statement and tips for writing efficient and readable programs have been provided. Besides standard features of the language, some of the recent additions like Array Handling Intrinsics, Enhancement in Dynamic Memory Management, IEEE Arithmetic Modules, Variable Length Strings, Interoperability with C Programming Language, Object Oriented Programming Support, Derived Type Enhancements and many other new features of the language have been incorporated.