Naturally occurring peptides and proteins consist almost exclusively of linear or cyclic polypeptide chains. Our group explores the chemical space of peptides by redesigning their topology through the introduction of branching points in the peptide chain. Branched peptides are generally resistant to proteolysis and display remarkable biological properties by multivalency effects (peptide dendrimers) and conformational rigidity (polycyclic peptides). We review our recent progress in peptide dendrimers as enzyme models, biofilm inhibitors, antimicrobials, DNA transfection and cell-penetrating agents, and in the synthesis and characterization of bicyclic peptides as new scaffolds for drug design.