Aminocyclitols comprise an important group of compounds with remarkable biological activities. From a structural standpoint, aminocyclitols are amino polyhydroxy cycloalkanes that can be found in nature in several families of natural products. Among them, the aminoglycoside antibiotics, since the discovery of streptomycin, have become particularly relevant at the forefront of the antibacterial treatment. Another group of aminocyclitols, generally referred to as aminocarbasugars, have been found as key structural components of some families of alkaloids that have evolved as suitable leads for the development of potent glycosidase inhibitors with a vast array of applications in medicinal chemistry, both as therapeutically useful agents as well as valuable pharmacological tools. On the other hand, the aminocyclitol moiety has been used by medicinal chemists as a versatile scaffold in drug design. Thus, in the antiviral arena, it is found as the key component of several families of carbocyclic nucleoside analogues, designed as metabolically stable surrogates of the natural nucleosides. Finally, in a still relatively unexplored area, some aminocyclitol derivatives are being used as key components of artificial receptors for which promising applications in drug research can be envisaged. In all cases, the development of the modern regio- and stereoselective synthetic methodologies enables a large variety of stereochemically defined aminocyclitol analogues in order to study in depth the influence of this moiety on the structure-activity relationships from a given lead.