Herculano’s family had humble origins. One of his grandfathers was a foreman stonemason in the royal employ. Herculano received his early education, comprising Latin, logic and rhetoric, at the Necessidades Monastery, and spent a year at the Royal Marine Academy studying mathematics with the intention of entering on a commercial career. In 1828 Portugal fell under the absolute rule of D. Miguel, and Herculano, becoming involved in the unsuccessful military pronunciamento of August 1831, had to leave Portugal clandestinely and take refuge in England and France. In 1832 he accompanied the Liberal expedition to Terceira Island as a volunteer, and was one of D. Pedro’s famous army of 7,500 men who landed at Mindelo and occupied Porto. He took part in all the actions of the great siege, and at the same time served as a librarian in the city archives. He published his first volume of verses, A Voz de Propheta, in 1832, and two years later another entitled A Harpa do Crente.

Privation had made a man of him, and in these little books he proves himself a poet of deep feeling and considerable power of expression. The stirring incidents in the political emancipation of Portugal inspired his muse, and he describes the bitterness of exile, the adventurous expedition to Terceira, the heroic defence of Porto, and the final combats of liberty. In 1837 he founded the Panorama in imitation of the English Penny Magazine, and there and in Illustração he published the historical tales which were afterwards collected into Lendas e Narrativas; in the same year he became royal librarian at the Ajuda Palace, which enabled him to continue his studies of the past. The Panorama had a large circulation and influence, and Herculano’s biographical sketches of great men and his articles of literary and historical criticism did much to educate the middle class by acquainting them with the story of their nation, and with the progress of knowledge and the state of letters in foreign countries.

After spending his early years as a poet, Herculano introduced the historical novel into Portugal in 1844 by a book written in imitation of Walter Scott. Eurico treats of the fall of the Visigothic monarchy and the beginnings of resistance in the Asturias which gave birth to the Christian kingdoms of the Iberian Peninsula. A second book, Monge de Cister, published in 1848, describes the time of King João I, when the middle class and the municipalities first asserted their power and elected a king who stood in opposition to the nobility.

The difficulties he encountered in producing it were very great, for the foundations had been ill-prepared by his predecessors, and he was obliged to be artisan and architect at the same time. He had to collect manuscripts from all parts of Portugal, decipher, classify and weigh them before he could begin work, and then he found it necessary to break with precedents and destroy traditions. Serious students in Portugal and abroad welcomed the book as an historical work of the first rank, for its evidence of careful research, its able marshalling of facts, its scholarship and its painful accuracy, while the sculptural simplicity of the style and the correctness of the diction made it a Portuguese classic. The second volume of his history appeared in 1847, the third in 1849, and the fourth in 1853.

In 1856 Herculano began editing a series of Portugalliae monumenta historica, but personal differences between him and the keeper of the Archives, which he necessarily frequented, interrupted his historical studies. On the death of his friend King Pedro V, Herculano left the Ajuda and retired to a country house near Santarém.

In 1866, Herculano married an old love of his, Mariana Hermínia de Meira, born about 1830, with whom he had no children.