Primero (in English also called Primus, in French Prime, in Italian Primiera or in Spanish Primera), is a 16th-century gambling card game of which the earliest reference dates back to 1526. Primero is closely related to the game of primo visto (a.k.a. prima-vista, and various other spellings), if not the same. It is also believed to be one of the ancestors to the modern game of poker, to which it is strikingly similar.

The gambling game with this name goes back to the 16th century, being known to Gerolamo Cardano as primiera, which he thought of as the noblest of all card games, to François Rabelais as prime, and to William Shakespeare as primero.

It is uncertain if Primero is of Spanish or Italian origin. Although Daines Barrington is of the opinion that it is of Spanish origin, a poem of Francesco Berni is the earliest known writing to mention the game; it affords proof that it was at least commonly played in Italy at the beginning of the 16th century. His work entitled Capitolo del Gioco della Primiera, published in Rome in 1526, and believed to be the earliest extant work describing a card game, contains some particulars on primero. According to David Parlett, the game's card-point system is found in other Italian games but nowhere else. The game is still very much played in central Europe and Spain with Italian-suited cards, under the name of goffo or bambara, remaining the major native vying game of Italy. Alessandro Striggio's madrigal dramatizing a party of the game "II gioco di primiera" was published in 1569.

This old game of cards was called prime in France, primera in Spain, and primiera in Italy. All names derived from the Latin primarius, 'first'. In English literature, besides the occasional use of the foreign names, the game is designated primero (and also prima-vista, a probable variant), with the usual corruptions in spelling of the early days.

According to Stephen Skinner, primero and prima-vista are one and the same game. As for John Minshew, primero and prima-vista (Primum et primum visum, that is, first and first seen, because he that can show such an order of cards, wins the game), are two different games of cards.

Whichever opinion these two seventeenth-century lexicographers might have had on the origin of primero, it seems fairly plausible that the game being played in different parts of Europe had to acquire similar names as it migrated from one country to another, or from one region to the other, notably in Italy and Spain. And with the addition of new rules to the original set of rules, or even variations on the rules that the game devised, it finally reached a level of development that made them become separate games, despite their common origin. So, as the Italian writer Berni said: "The game is played differently in different places."

Daines Barrington described an Elizabethan card party painted by Federico Zuccari that originally belonged to Lord Falkland in which Lord Burleigh is represented playing at cards with three other persons, apparently of distinction, each having two rings on the same fingers of both their hands. The cards used are marked as at present, although they differ from those of modern times for being narrower and longer. Eight of the cards lie on the table with the blank side uppermost, for the cards at that time had blank backs, while four remain in each of the other players hands. A particular in this painting is that one of the players is seen showing his cards, which are: the jack (knave) of hearts, the ace, 7 and 6 of clubs. The cover of the pack lying on the table displays two lions supporting a shield, upon which is what appears to be a heraldic rose (the crest of the Tudors), and underneath, though indistinctly, the partially illegible name of a French card-maker Jehan Licl**rer. This particular shows that the cards then used were at least sometimes obtained from France. The money on the table, together with considerable heaps of gold and silver, appears to be coins of Edward VI and Queen Elizabeth I.

As the first Marquess of Exeter, Lord Burleigh, is said to have entirely devoted his time to business and study, taking no diversion but that afforded by his gardens, of which he was both fond and proud, it is to be supposed that this painting was not actually a portrait of him, though mistaken for his, as was the ownership of the old manor-house of Wimbledon. So, there seems to be little doubt here as for which game the artist meant to describe, and that the person exhibiting his cards to the spectators had won a lush, for his three clubs are the best cards for counting.