| Conflict: | Siege of Zoutleeuw |
| Partof: | the War of the Spanish Succession |
| Date: | Investment: 29 August – 5 September 1705 Siege: 31 August – 5 September 1705 |
| Place: | Zoutleeuw, Flemish Brabant, Belgium |
| Result: | Allied victory |
| Combatant1: | Allies |
| Commander1: | Lieutenant general Dedem |
| Commander2: | Brigadier general Dumont |
| Strength1: | 10,000 men 16 artillery pieces |
| Strength2: | 400 men 18 guns 2 mortars |
| Casualties1: | Light |
| Casualties2: | 400 men captured or killed 20 guns and mortars captured |
The siege of Zoutleeuw or the siege of Léau (29 August 1705 – 5 September 1705) was a siege of the War of the Spanish Succession. Allied troops with 16 artillery pieces under the command of the English Captain general the Duke of Marlborough, besieged and captured the small French-held Brabantine fortified town of Zoutleeuw in the Spanish Netherlands.
After piercing the French fortified lines Lines of Brabant at Elixheim on 18 July 1705, the Duke of Marlborough found his plans to bring the French army under Duc de Villeroi to a decisive battle frustrated by the French refusal to engage, their extensive use of field fortifications and the unwillingness of the Dutch Field Deputies to submit to his plans. The Allies contented themselves by widening the breach in the lines of Brabant by capturing Zoutleeuw to the north of Eliksem on 5 September. Zoutleeuw had been hastily abandoned by the French troops of the Duke of Berwick in July, after the Allied capture of Huy, with gaps being blown up in the walls.
Zoutleeuw, surrounded by swamps, was taken by a small detachment of 15 battalions and 15 squadron's with 16 artillery pieces under the command of lieutenant general Dedem. The town was invested on 29 August and trenches were opened on 31 August. The Allied siege train arrived from Maastricht on 3 September. That same night, the besiegers attacked and captured a redoubt with little opposition. The infantry battalions carried the trenches within 100 yards of the town, the siege artillery quickly following them.
Before the Allied artillery batteries could open fire, the French governor brigadier general Dumont decided to surrender on 4 September after Dedem threatened to kill the entire garrison of 400 men if they continued to resist. The town and citadel were occupied by 200 Allied troops on 5 September. The garrison marched out on 7 September to become prisoners of war in Maastricht, the officers being allowed to retain their swords and baggage.
The Allies took 10 bronze guns, eight iron guns, two bronze mortars, 10,000 grenades, 200 barrels of gunpowder, 6,000 tools, 2,000 muskets, 100 barrels of musket balls and 18,000 sacks of flour.
The siege was the last major Allied operation near the Meuse river as the strong French fortresses of Namur and Charleroi and more tempting targets in Brabant discouraged them from moving upriver. Marlborough had the Lines of Brabant levelled and the town of Tirlemont dismantled.