This research project explores an area which had been touched only tangentially, being a comparative analysis of the idea and interpretations of friendship which emerge from the three vernacular collections attributed to the supervision of King Alfonso X of Castile (1252-1284): namely the Marian songs Cantigas de Santa María, the law code known as the Siete Partidas and the chronicle Estoria de España. These sources have been examined by adopting a thematic approach which has highlighted the existence of categories such as spiritual, religious and political friendships, as well as other forms of amicable relationships, including those between representatives of different religious, ethnic and social groups. Additionally, this study demonstrates that there was a conscious adoption of a specific lexicon of amicitia which contributed to reinforce either the opposition or the coincidence between friendship, companionship and counsellorship. Despite the undeniable inheritance of both classical eastern and western traditions, the works of the ‘Learned’ King present a peculiar idea of friendship which was deeply affected by contemporary historical contingencies and by the political and cultural projects of a sovereign who wanted to be regarded as a friend of his people, without denying, however, the unbridgeable gap which existed between different social groups. Interestingly, even if the Alfonsine works display a complicated range of relationships which envisage clear differences, they still outline a perfectly-balanced system within which the general and untouchable rules of friendship predominated, although in some cases certain variants were allowed in order to adapt such general requirements to contemporary social and political situations.