Disclosed herein are compounds having activity as cell penetrating peptides. In some examples, the compounds can comprise a cell penetrating peptide moiety and a cargo moiety. The cargo moiety can comprise one or more detectable moieties, one or more therapeutic moieties, one or more targeting moieties, or any combination thereof. In some examples, the cell penetrating peptide moiety is cyclic. In some examples, the cell penetrating peptide moiety and cargo moiety together are cyclic. In some examples, the cell penetrating peptide moiety is cyclic and the cargo moiety is appended to the cyclic cell penetrating peptide moiety structure. In some examples, the cargo moiety is cyclic and the cell penetrating peptide moiety is cyclic, and together they form a fused bicyclic system.
