The use of metal organic frameworks (MOFs) as catalytic nanoreactors is thoroughly reviewed. Two approaches can be followed for the encapsulation of catalytically active species into the scaffold of a MOF: (i) ship in a bottle and (ii) bottle around a ship. In the first case, formation of metallic nanoparticles or metal oxides are among the most studied systems, and metal precursor impregnation followed by reduction/oxidation is the widely used synthetic strategy. Also worth mentioning are the few examples of enzyme encapsulation. On the other hand, bottle around a ship has been used when the active phase is added to the MOF synthesis and in situ encapsulated. The most studied example has been described for heteropolyacids, where templating effects have been discovered. The encapsulation of other macromolecules, such as porphyrins, illustrate the great opportunities that MOFs offer for direct encapsulation. The confinement of the active sites affects their catalytic behaviour when compared with their homogeneous counterparts, in most cases enhancing both conversion and selectivity to the desired products. In addition, confined active sites are protected from deactivation by leaching or aggregation, thus facilitating catalyst reusability.