General Jacobus Herculaas de la Rey (22 October 1847 - 15 September 1914), known as Koos de la Rey was a Boer general during the Second Boer War and is widely regarded as being one of the strongest military leaders during that conflict.

He is generally regarded as the bravest of the Boer generals during the Second Boer War and as one of the leading figures of Boer independence. As a guerrilla, his tactics proved extremely successful. De la Rey opposed the war until the last, but when he was once accused of cowardice during a Volksraad session, he replied that if the time for war came, he would be fighting long after all those clamoring for war had given up. This proved to be the case.

De la Rey fought in the Basotho War of 1865 and Sekhukhune's War of 1876. He did not take a very active part in the First Boer War, but as field cornet in the western Transvaal, he took over Piet Cronje's Potchefstroom siege when Cronjé fell ill. He was elected commandant of the Lichtenburg district, and became a member of the Transvaal Volksraad in 1883. A supporter of the progressive faction under General Piet Joubert, he opposed Paul Kruger's policies against the uitlanders, the foreigners who flocked to the Transvaal gold-rush, and warned it would lead to war with Britain.

On 15 September 1914 an old comrade General C.F. Beyers, Commandant-General of the armed forces, resigned his commission and sent his car to fetch De la Rey from Johannesburg to Pretoria as he wished to consult with him. The two generals then set out that evening for Potchefstroom military camp where General JCG Kemp had also resigned. They encountered several police roadblocks but refused to stop, although they had in fact been set to capture the Foster gang.[2] At Langlaagte the police fired on the speeding car and a bullet struck De la Rey's back, ending his life;[2] his last words were dit is raak ('It hit'). He returned to his Lichtenburg farm as van Rensburg had predicted. Many Boers were convinced he had been deliberately assassinated, while others could not believe that he would have joined a rebellion, breaking his oath. According to Beyers the plan was to co-ordinate the simultaneous resignation of all the senior officers in protest at the attack on South West Africa. The theory of a government assassination holds sway to this day.