Giambattista Marino (also Giovan Battista Marino) (18 October 1569 – 25 March 1625) was an Italian poet who was born in Naples. He is most famous for his long epic L'Adone.

The Cambridge History of Italian Literature thought him to be "one of the greatest Italian poets of all time". He is considered the founder of the school of Marinism, later called Secentismo, characterised by its use of extravagant and excessive conceits. Marino's conception of poetry, which exaggerated the artificiality of Mannerism, was based on an extensive use of antithesis and a whole range of wordplay, on lavish descriptions and a sensuous musicality of the verse, and enjoyed immense success in his time, comparable to that of Petrarch before him.

He was widely imitated in Italy, France (where he was the idol of members of the précieux school, such as Georges Scudéry, and the so-called libertins such as Tristan l'Hermite), Spain (where his greatest admirer was Lope de Vega) and other Catholic countries, including Portugal and Poland, as well as Germany, where his closest follower was Christian Hoffmann von Hoffmannswaldau. In England he was admired by John Milton and translated by Richard Crashaw.

He remained the reference point for Baroque poetry as long as it was in vogue. In the 18th and 19th centuries, while being remembered for historical reasons, he was regarded as the source and exemplar of Baroque "bad taste". With the 20th century renaissance of interest in similar poetic procedures his work has been reevaluated: it was closely read by Benedetto Croce and Carlo Calcaterra and has had numerous important interpreters including Giovanni Pozzi, Marziano Guglielminetti, Marzio Pieri and Alessandro Martini.

Marino remained in his birthplace Naples until 1600, leading a life of pleasure after breaking off relations with his father who wanted his son to follow a career in law. These formative years in Naples were very important for the development of his poetry, even though most of his career took place in the north of Italy and France. Regarding this subject, some critics (including Giovanni Pozzi) have stressed the great influence on him exerted by northern Italian cultural circles; others (such as Marzio Pieri) have emphasised the fact that the Naples of the time, though partly in decline and oppressed by Spanish rule, was far from having lost its eminent position among the capitals of Europe.

Marino's father was a highly cultured lawyer, from a family probably of Calabrian origin, who frequented the coterie of Giambattista Della Porta. It seems that both Marino and his father took part in private theatrical performances of their host's plays at the house of the Della Porta brothers. But more importantly, these surroundings put Marino in direct contact with the natural philosophy of Della Porta and the philosophical systems of Giordano Bruno and Tommaso Campanella. While Campanella himself was to oppose "Marinism" (though not attacking it directly), this common speculative background should be borne in mind with its important pantheistic (and thus neo-pagan and heterodox) implications, to which Marino would remain true all his life and exploit in his poetry, obtaining great success amongst some of the most conformist thinkers on the one hand while encountering continual difficulties because of the intellectual content of his work on the other.

Other figures who were particularly influential on the young Marino include Camillo Pellegrini, who had been a friend of Torquato Tasso (Marino knew Tasso personally, if only briefly, at the house of Giovan Battista Manso and exchanged sonnets with him). Pellegrini was the author of Il Carrafa overo della epica poesia, a dialogue in honour of Tasso, in which the latter was rated above Ludovico Ariosto. Marino himself is the protagonist of another of the prelate's dialogues, Del concetto poetico (1599).

Marino gave himself up to literary studies, love affairs and a life of pleasure so unbridled that he was arrested at least twice. In this as in many other ways, the path he took resembles that of another great poet of the same era with whom he was often compared: Gabriello Chiabrera. But an air of mystery surrounds Marino's life, especially the various times he spent in prison; one of the arrests was due to procuring an abortion for a certain Antonella Testa, daughter of the mayor of Naples, but whether she was pregnant by Marino or one of his friends is unknown; the second conviction (for which he risked a capital sentence) was due to the poet's forging episcopal bulls in order to save a friend who had been involved in a duel.

But some witnesses, who include both Marino's detractors (such as Tommaso Stigliani) and defenders (such as the printer and biographer Antonio Bulifoni in a life of the poet which appeared in 1699) have firmly asserted that Marino, much of whose love poetry is heavily ambiguous, had homosexual tendencies. Elsewhere, the reticence of the sources on this subject is obviously due to the persecutions to which "sodomitical practices" were particularly subject during the Counterreformation.

Marino then fled Naples and moved to Rome, first joining the service of Melchiore Crescenzio, then that of Cardinal Aldobrandini. In 1608 he moved to the court of Duke Carlo Emanuele I in Turin. This was not an easy time for the poet, in fact he was the victim of an assassination attempt by his rival Gaspare Murtola and he was then sentenced to a year in prison for malicious gossip he had written about the duke.

In 1615 he left Turin and moved to Paris, where he remained until 1623, honoured by the court and admired by French literary circles. He returned to Italy in triumph and died in Naples in 1625.