Halogenated compounds, containing F, Cl, Br or I represent not only important pollutants’ but are also used in a variety of applications such as solvents, flame retardants, surface modification, antifouling, pesticides and as active ingredients in health care from blood extenders to anticancer drugs. Halogenated compounds have become particularly important in higher value added pharmaceutical and agrochemical products. It is estimated that 20 percent of all pharmaceutical small molecule drugs and ~30 percent of all active compounds in agrochemistry are halogenated. Chemical halogenation is a well-established technology. But procedures are typically characterised by hazardous or even highly toxic chemicals and poor atom economy. It seems obvious to periodically assess how biological halogenation can offer an advantage over chemical halogenation. The marine biosphere is a promising source for halogenating organisms and enzymes. This review is timely as several large marine biodiversity programmes have been launched for bio prospecting for novel halogenases.