The Congress of Laibach was a conference of the allied sovereigns or their representatives, held in 1821 as part of the Concert of Europe, which was the decided attempt of the Great Powers to settle international problems after the Napoleonic Wars through discussion and collective weight rather than on the battlefield.
The Congress was held in Laibach (modern day Ljubljana) in what is now Slovenia but was then a part of the Austrian Duchy of Carniola, from January 26 until May 12, 1821. Before the break-up of the Congress of Troppau it had been decided to adjourn it until the following January, and to invite the king of Naples, Laibach being chosen as the place of meeting. Castlereagh, in the name of Britain, had cordially approved this invitation, as implying negotiation and therefore as a retreat from the position taken up in the . Before leaving Troppau however, the three autocratic powers, Russia, Austria and Prussia, had issued, on the December 8, 1820, a circular letter, in which they reiterated the principles of the Protocol, i.e. the right and duty of the powers responsible for the peace of Europe to intervene to suppress any revolutionary movement by which they might conceive that peace to be endangered (Hertslet, No. 105). Against this view Castlereagh once more protested in a circular dispatch of January 19, 1821, in which he clearly differentiated between the objectionable general principles advanced by the three powers, and the particular case of the unrest in Italy, the immediate concern not of Europe at large, but of Austria and of any other Italian powers which might consider themselves endangered (Hertslet, No. 107).
The conference opened on January 26, 1821, and its constitution emphasized the divergences revealed in the above circulars. The emperors of Russia and Austria were present in person, and with them were Counts Nesselrode and Capodistria, Metternich and Baron Vincent; Prussia and France were represented by plenipotentiaries. Britain, on the ground that she had no immediate interest in the Italian question, was represented only by the Lord Stewart, the ambassador at Vienna, who was not armed with full powers, his mission being to watch the proceedings and to see that nothing was done beyond or in violation of the treaties. Of the Italian princes, Ferdinand of Naples and the duke of Modena came in person; the rest were represented by plenipotentiaries. It was soon clear that a more or less open breach between Britain and the other powers was inevitable. Metternich was anxious to secure an apparent unanimity of the powers to back the Austrian intervention in Naples, and every device was used to entrap the British representative into subscribing a formula which would have seemed to commit Britain to the principles of the other allies. When these devices failed, attempts were made unsuccessfully to exclude Lord Stewart from the conferences on the ground of defective powers. Finally, he was forced to an open protest, which he caused to be inscribed on the journals, but the action of Capo d'Istria in reading to the assembled Italian ministers, who were by no means reconciled to the large claims implied in the Austrian intervention, a declaration in which as the result of the intimate union established by solemn acts between all the European powers the Russian emperor offered to the allies the aid of his arms, should new revolutions threaten new dangers, an attempt to revive that idea of a universal union based on the Holy Alliance against which Britain had consistently protested. The objections of Britain were, however, not so much to an Austrian intervention in Naples as to the far-reaching principles by which it was sought to justify it. King Ferdinand had been invited to Laibach, according to the circular of 8 December, in order that he might be free to act as mediator between his erring peoples and the states whose tranquillity they threatened. The cynical use he made of his freedom to repudiate obligations solemnly contracted is described elsewhere (see Naples, History). The result of this action was the Neapolitan declaration of war and the occupation of Naples by Austria, with the sanction of the congress. This was preceded, on 10 March, by the revolt of the garrison of Alessandria and the military revolution in Piedmont, which in its turn was suppressed, as a result of negotiations at Laibach, by Austrian troops.