Resident Commissioner is the title of several, quite different types of Commissioner in overseas possession or protectorate of the British Crown or of the United States of America.
Resident Commissioners appointed by the British crown typically reside in the territorial unit of which they are in charge. This also the case with most otherwise styled Commissioners.
Notably in certain complex colonial units within the British Empire, the High Commissioner to whom was given the highest 'regional' supervision (either residing in one of the constitutive territories, e.g. in the British Western Pacific Territories (BWPT), first by the Governor on Fiji, then from 1952 onwards on the Solomon Islands; or even in a neighbouring colony, e.g. the Governor of the Straits Settlements as High Commissioner for the Federated Malay States) would commonly be represented in territories not comprising his residence by a Resident Commissioner, though in some places (including some of the Federated Malay States) similar officials were formally styled as Residents, a more diplomatic title; otherwise another type of official was also possible (e.g. the British Consul in the protected state of Tonga, a Polynesian kingdom; an Administrator on Nauru; a mere Chief Magistrate on tiny Pitcairn). In some cases one could compare his task to the Lieutenant-Governor of a minor colony, especially as the High Commissioner indeed could be a British colonial Governor doubling as such.
In the British Western Pacific Territories this was the case for:
While the post of High Commissioner for Southern Africa (HCSA) was held 27 January 1847 - 31 May 1910 by the Governors of the Cape Colony, then till 6 April 1931 by the Governors-General of the Union of South Africa, after that date filled separately till 1963, there have been resident representatives in the constituent territories:
In India, a Resident Commissioner is the representative of the State Government with an office in New Delhi, who is also supposed to manage the reception of state government functionaries who visit New Delhi. He coordinates with various Ministries of the Central Government, Central PSUs, multi-lateral and bilateral agencies and various other organisations on behalf of the state government. he is an IAS Officer.