'MG3' was a British naval undertaking associated with 'Callboy' (i) and designed to ensure the safe passage of a 'convoy' from Malta (October 1941).

In fact the ships involved did not sail as a convoy but as independents. The first of these, which departed Malta for Gibraltar on 16 October, were the 9,653-ton Clan MacDonald and 5,641-ton Empire Guillemot: the former reached Gibraltar on 19 October, while the latter suffered engine problems, turned back to Malta and departed again on 22 October only to be sunk by an air-launched torpedo off Galeta island on 24 October. The last of these three ships was the 7,347-ton Clan Ferguson, which departed on 24 October but was spotted by Italian aircraft and returned to Malta.