Nanosystems with combined magnetic and plasmonic functionalities have in recent years become an active topic of research. By an adequate internal architecture of the constituting components, the magneto‐optical activity of these systems can be greatly increased due to the electromagnetic field enhancement associated with the plasmon resonance. Simultaneously, the magnetic functionality permits the control of the plasmonic properties by an external magnetic field, which allows the development of active plasmonic devices. These materials find applications in, for example, gas and biosensing areas, and in integrated photonic devices for telecommunications. In the present work the state of the art and current understanding of the phenomenology associated with magnetoplasmonic structures where magnetism and plasmonics are intertwined are reviewed. Magnetoplasmonic systems possess both plasmonic and magnetic functionalities. By a smart combination of plasmonic and ferromagnetic materials with magnetooptical activity it is possible to design nanostructures whose magneto‐optical properties are enhanced by plasmon resonance excitation, and whose plasmonic properties are modulated by an external magnetic fi eld. These structures fi nd applications in sensing devices as well as in optical communications.