Willem Vleertman (1 August 1658 – 23 April 1742) was a Dutch States Army officer and engineer who played an important role in various conflicts in the late 17th and early 18th centuries.

Beyond his military exploits, Vleertman contributed to engineering projects, including the establishment of postal services and infrastructure improvements, and in 1717 saved Amsterdam from a flood.

In 1688, he accompanied William III during the Glorious Revolution and subsequently, on the orders of the king, introduced an improved postal service between the Dutch Republic and Vienna.

Upon his return to England, he witnessed the Williamite War in Ireland and, after the Battle of the Boyne, served as a courier for William III to convey news of the victory.

In 1691, he established a postal service from Maastricht to Brussels, through Aachen to Cologne, and in the same year served as a captain in the Dutch army in Brigadier Hol's regiment in Brabant.

In July 1692, he once again acted as a courier for William III, announcing to the Viennese court and the Porte that His Majesty and the States-General were offering their mediation to end the war between the two countries.

The military council acquitted him, and the main instigators of the riot were sentenced to publish in newspapers and on the streets that all the rumors they had spread about Vleertman were slanderous.

Here, General François Nicolas Fagel tasked him with cutting off the water supply to the city, which he succeeded in doing, and he was put in charge of the artillery and siege works on the left flank.

In 1705, Vleertman was once again with the Dutch army, witnessing the second Allied siege of Huy in July and participating in actions at Gheete, Diest, and Aarschot.

By January 1706, he was already in the field again, at Maastricht; on 26 May, he brought news of the victory at Ramillies to The Hague, and on 1 June, he went to Düsseldorf on the orders of Daniël van Dopff to report.

In 1710, the Burgomasters of Amsterdam allowed him to undertake another "Field Expedition," and he proved his skills as a capable engineer during the sieges of Douai, Béthune, St. Venant, and Aire.

In 1714, he served King Frederick William I of Prussia and in 1715, during the Siege of Stralsund, he was in charge of supplying the besieging artillery and building a bridge of gabions over the moat.

By capturing the renowned Georg Heinrich von Görtz, minister of Charles XII of Sweden, on 20 February 1717 in Arnhem, he once again demonstrated his promptness, while in December 1717, he prevented Amsterdam from flooding by installing a cistern on the Haarlemmerdijk when it was threatened by the surging seawater.

In 1721, he again acted as a courier, delivering a portrait of George I of England to Arnhem, which the king offered to the city government as thanks for arresting Görtz.

In 1728, he greatly served Dutch trade by preventing the establishment of a competing East India Company in Altona, Hamburg.