In the Ancien Régime, villages and provinces established direct lines of communication with the Crown through representatives and emissaries. This work analyses the progressive institutionalisation of the representative agents of frontier territories under the Habsburgs, specifically the Basque provinces of Guipúzcoa and Álava and the Señorío of Vizcaya. Some of the main issues dealt with in this comparative study are the corporative and representative nature of these diplomatic offices, their simultaneous function as a government instrument for the Crown, and the consolidation of a decentralised administrative apparatus under the control of local elites.