This text on "Operator Frames in Hilbert Spaces" for students and researchers are self-contained and give more and comprehensive coverage of the topics like Frames, K-frames, g-frames and kg-frames. This book is divided in to five chapters. the first chapter contains brief introduction of this book. Chapter 2 Presents basic information of frames, Bessel sequences, Riesz basis, types of frames in Hilbert spaces and frame operator, Chapter 3 contains the definitions of different types of K- frames and examples, frame operators of K-frames, and some results on K-frame operators are established....