His father was Marthinus Steyn and his mother Cecilia Wessels. He first attended a farm school and then went to Grey College, Bloemfontein. At the suggestion of Judge James Buchanan he continued his education at Deventer in the Netherlands. Before sitting for the admission examination to the University of Leyden he decided on legal training at the Inner Temple in London, where he was admitted early in the 1880's. In 1882 he was called to the bar. He now returned to Free State and soon had a flourishing practice in Bloemfontein. On 10 March 1887 he married Rachel Isabella (Tibbie) Fraser. His public career began in 1889 with his appointment as Attorney-General. He rose rapidly through the ranks and on 5 May 1892 he was promoted to first criminal judge.
When FW Reitz resigned as president in 1895 Steyn seemed to be the obvious choice for the succession. J.G. Fraser, the other candidate opposed closer cooperation with the South African Republic (ZAR), while Steyn supported it. The Jameson Raid put the result beyond any doubt. Steyn won and was sworn in as president on 4 March 1896. Although he was just 39 years old his decisions and the naturalness with which he adapted to his high position bore testimony to an already mature attitude to life. He also displayed a strong sense of mission and duty.
Closer cooperation with the South African Republic did not exclude cooperation with the rest of South Africa. Steyn believed that, after the Jameson Raid, political feeling in the Cape Colony supported the republics. Sir Alfred Milner, the new British High Commissioner soon challenged this relationship as he was an ardent imperialist. From 1896 onwards he was busy with the strengthening of the loyalty and political cohesion of the English-speaking South Africans and to channeling Uitlander discontent and opposition to Kruger's government. Steyn, however, considered British imperialism a danger to the independence of the Orange Free State. At a conference in Bloemfontein in March 1897, attended by Pres Kruger, Steyn proposed that they should extend the political alliance of 1889 by adding a clause to the effect that the two governments would consult with each other on all matters that could lead to war with Great Britain.
Steyn attempted to persuade the Transvaal government to become more flexible in their policies regarding Uitlander franchise and the dynamite monopoly. In 1899 the situation came to a head when Milner broke off talks with Kruger about the franchise question during the Bloemfontein Conference (31 May-5 June 1899) - a meeting instigated by Steyn. War was now clearly imminent. On 27 September 1899 he presented to the Free State Volksraad a clear and final report on the negotiations and concluded that he would rather lose the independence of the Free State with honour.
During the first months of the war he solved innumerable problems and visited the commandos to encourage his burghers. After the catastrophic surrender of general Piet Cronje at Paardeberg Steyn called on the demoralised burghers to make a determined stand: first at Poplar Grove (07/03/1900) and then at Abrahamskraal (10/03/1900) but without success.
On 13 March Lord Roberts entered Bloemfontein. Steyn and the government had left Bloemfontein on the 12th. At Kroonstad Steyn was chairman of a joint Council of War where Kruger and General Piet Joubert were also present. Here they decided to abolish wagons and to employ mounted commandos in future thus giving the Boers increased mobility.
The OFS government now had to fall back repeatedly before the advance of Lord Roberts.
When Bethlehem fell into British hands on 7 July the seat of the government was
"in the field." Steyn and his executive council now remained with De Wet throughout the war.
Steyn often had to intervene when Transvaal wished to open negotiations with the British. In May 1900 he went to Pretoria to encourage a dejected president Kruger. When peace negotiations were mentioned Steyn remained adamant that the war was to continue. At Senekal a deeply upset Steyn heard about Botha's negotiations with Kitchener at Middelburg (28/02/1901). Although nothing came of this, it was a clear indication that Transvaal's resolve to continue with the war was again wavering. Steyn met with the Transvaal government at Klipdrif near Vrede and they decided to continue with the struggle. After being informed of another round of negotiation between the ZAR and Kitchener in May 1901 he forcefully protested that the OFS had not been consulted about the meeting with the Transvalers at Waterval.
On 31 October 1900 he rejoined De Wet in the Western Transvaal. and returned with him to the Orange Free State. Near Bothaville they almost fell into the enemys hands. In December Steyn accompanied De Wet during his first unsuccessful attempt to invade the Cape Colony. He also accompanied De Wet during his second abortive attempt to invade the Cape Colony in 10 February 1901.
When his term of office expired he insisted that they should hold a presidential election. Steyn was the only candidate and at Doornberg they solemnly administered the oath of office and reconstituted the executive council.
On 11 July 1901, Steyn, through the efforts of Ruiter, his personal servant, managed to evade capture at Reitz. His bodyguard and the members of his government however were captured and he had to reconstitute his cabinet.
Steyn's official replies to British proclamations were legally well-reasoned, and were worded in a way that encouraged the burghers. On 19 March 1900 the President delivered his answer to Roberts's annexation of the Free State. In this he solemnly declared that the republic of the Free State still existed, despite the so-called annexation. On 7 August 1901 there was another one of Kitchener's threatening proclamations in which all who did not surrender before 15 September were threatened with banishment and confiscation of property. In Steyn's reply of 15 August he pointed out to Kitchener his inadmissible methods of warfare.
After a few Republican victories towards the end of 1901, e.g. Tafelkop (20 December) and Groenkop (25 December) Steyn joined the commando of General de la Rey at Doornspruit in March 1902 to consult Dr von Rennenkampf about his eyes, which showed the first symptoms of the serious disease that subsequently afflicted him. Here Acting President Schalk Burger informed him that the first steps towards final negotiations for peace were under way. On 9 April 1902 the governments of the two republics met at Klerksdorp. Although his legs were already semi-paralysed, his will remained indomitable. His only condition for peace was the retention of independence. When the governments met Kitchener on 12 April at Pretoria it was decided to summon representatives of the burghers in the field, because only the people, according to the constitutions of the republics, could decide the question of their independence. Kitchener was extremely impressed by Steyn and said of him: "He is head and shoulders above the others, and has great influence." On 15 May, when he arrived at Vereeniging he was almost totally paralysed. He only attended two meetings but Rev J.D. Kestell and his generals kept him informed and consulted him regularly. On 29 May, he left for Kroonstad where medical attention was available. He resigned as president and was thus spared the bitterness of signing the treaty of Vereeniging. By the time his wife joined him on 11 June 1902 he was completely helpless. With the financial aid of friends they left for Europe to seek medical aid for his condition. For the next three years Prof. C. Winkler and various other physicians treated Steyn. In 1903 he had recovered sufficiently to return home where they settled at Onze Rust.
He welcomed self-government in 1907 as the movement for a united South Africa was very dear to him. Steyn was to serve as one of the Free State delegates at the National Convention at Durban in October/November 1908, where he was elected vice-chairman. He exercised great influence both in and out of the conference hall. He was a candidate for the premiership but because of health reasons he declined and retired to his farm. He, however, was not aloof from national affairs. His door was always open and friends and leaders often sought his advice.
On 16 December 1913 the National Women's Memorial for which he, more than anyone else, had worked, was unveiled in Bloemfontein. On 28 November 1916 he died suddenly while addressing the Oranje Vrouevereniging in the Memorial Hall in Bloemfontein. He is buried at the foot of the Women's Memorial.