The first Westerners to reach Vietnamese shores were likely traders from ancient Rome, who visited the ports of Champa around the 2nd century AD. Later, in the 13th century, Marco Polo sailed along the coast on his journey to China. However, the arrival of Portuguese merchant Antonio Da Faria at Fai Fo (modern-day Hoi An) in 1535 marked a more lasting impact. The Portuguese established a trading post at Fai Fo, then a bustling Southeast Asian port frequented by ships from China and Japan, and they were soon followed by other European maritime powers.

Alongside traders came missionaries who found receptive audiences, particularly among peasants and those at the lower levels of the Confucian social hierarchy. By the 1630s, however, the local elite felt increasingly threatened by Christian teachings, leading to a ban on missionary work and, at times, harsh punishments, including expulsions and executions of priests. Despite these restrictions, the Catholic Church continued to grow, and by the late 17th century, it claimed several hundred thousand converts across the region.

As regional factions divided Vietnam, European powers exploited the rivalry between the Nguyen and Trinh lords, exchanging weaponry for trading privileges. However, with the end of the civil conflict in 1674, foreign merchants lost their leverage, and gradually the English, Dutch, and French closed their trading posts, leaving only the Portuguese in Fai Fo.

By the late 18th century, Catholic missions became a gateway for French interests aiming to counterbalance Britain’s influence in Asia. When a large-scale rebellion erupted in Vietnam during the early 1770s, French entrepreneurs saw an opportunity to strengthen their foothold on the Indochinese peninsula, setting the stage for a deeper and more enduring French presence in the region.