The Battle of Kallo was a major field battle fought from 20 to 21 June 1638 in and around the forts of Kallo and Verrebroek, located on the left bank of the Scheldt river, near Antwerp, during the second phase of the Eighty Years' War. Following the symbolic recovery of Breda during the 1637 campaign, the Dutch Republic agreed with the French Crown, with whom it had allied in 1635, to besiege a major city in the Spanish Netherlands during the 1638 campaign. The commander of the Dutch States Army, Frederick Henry of Orange, planned an approach over Antwerp from the two sides of the Scheldt. Count William of Nassau-Siegen was entrusted to land in the Spanish-controlled Waasland region, west of Antwerp, to seize the forts of Kallo and Verrebroek, along with several other key fortifications, to invest Antwerp from the west. In the meantime, Frederick Henry would advance on the opposite bank to complete the blockade of the city while the armies of France invaded the Spanish Netherlands from the south to oblige the Spanish Army of Flanders to divide its forces.
The Dutch operation proceeded well at first, since the force under Nassau-Siegen easily captured Kallo and Verrebroek. However, it was unable to gain further progress, so the count entrenched his troops and asked for reinforcements. The governor of the Catholic Netherlands, the cardinal-infante Ferdinand, younger brother to Philip IV of Spain and victor of the Battle of Nördlingen, with an army consisting of tercios and other troops from several garrison duties, launched a counter-attack over the Dutch positions the night of 20–21 June. Advancing along three narrow fronts, the Spanish forces drove the States' soldiers from a series of outer works, but were unable to dislodge them from the two main forts. However, exhaustion and lack of supplies and reinforcements led Nassau-Siegen to order the re-embarkation during the next night. Ferdinand launched a second assault while the retreat was ongoing, and, as panic ensued among the Dutch ranks, the entire force was defeated. The Dutch commander escaped with a few hundred men, while many other drowned attempting to save themselves or were captured.
Along with the successful defense of Saint-Omer and Geldern that same year, the victory of Kallo proved that the Spanish tercios were still a formidable field force. Additionally, it was interpreted in terms of Catholic propaganda and became subject of paintings, poems and popular songs.