Peptides and proteins are crucial biomolecules in life. The manifold functions they carry out range from molecular recognition and signaling to catalysis and immune response. However, the native systems are limited to a reduced toolbox of chemical functionalities as well as tridimensional structures. Widening these toolboxes could pave the way to engineer peptides and proteins with enhanced properties compared to their native counterparts and/or with structures and functions unprecedented in Nature. Advances in the chemical and biological synthesis of peptides and proteins, in computational tools, in molecular biology and in high-throughput screening methods are making this realm possible. This book aims to give an overview of the last developments in the field of peptide and protein engineering. It comprises a collection of chapters that span from the production of simple non-proteinogenic building blocks and peptidic scaffolds of different sizes and structures to more complex systems including peptide-based nanomaterials, enzymes and artificial metalloenzymes. Different strategies are described where chemical and biological tools have been developed and combined to attain the desired properties and sought functionalities. The diverse systems described in this book highlight the progress in this important field and represent the starting points for the development of functional biomolecules, biomaterials and hybrid systems capable of addressing key societal challenges of our times in relevant areas such health, environment and energy.