Botha was born on the farm Telegraaf in the Paul Roux district of the Orange Free State, the son of Afrikaner parents. He was the only son of Pieter Willem senior (a widower with four children) and Hendrina Prinsloo/de Wet (a widow with five children). His father, also named Pieter, fought as a commando against the British in the Second Boer War (1899–1902). During the war his mother was interned in a British concentration camp.
Botha's early education was at Paul Roux. Later he attended secondary school in Bethlehem before entering the University of the Orange Free State in Bloemfontein to study law. It was here that his political career began. Initially he helped organize the National Party (NP) during by-election campaigns and also became campus branch chairman.
He was also a part-time reporter for Die Volksblad and a member of the Afrikaanse Nasionale Studentebond (National Afrikaans Student Association). At the age of twenty he delivered an address to Prime Minister Malan on his visit to the campus.
Malan was impressed and Botha was offered a post as party organizer in the Cape. He left the university before completing a degree in order to begin a full-time political career, a decision made when he was only 20 years old. He began working for the National Party as a political organiser in neighbouring Cape Province .
In the years leading to World War II, Botha sympathised with the German Nazi Party. In 1939 Botha, along with J. B. Vorster, helped to form the Cape Town branch of the Ossewabrandwag (Ox-wagon torch guard), where he served as a leader of the organisation. He was nearly interned by the military at one point, because of his pro-German stance. He became disillusioned with the Ossewabrandwag as a result of an internal split and, in August 1941, wrote a scathing letter to Die Burger attacking the organisation. He said that national socialism was ' volksvreemd ', meaning unknown, dangerous and contrary to the Christian nationalism of Afrikaners, and charged the Ossewabrandwag with 'interference' in national politics. He was expelled from the organisation four days later. Soon afterwards D. F. Malan ordered all members of the (NP) to withdraw from the Ossewabrandwag
Botha's political career bloomed and in 1946 he was promoted to Union Information Officer for the NP. One of his duties was to prepare circulars about the NP's policies and to spread propaganda and other information that might be favourably used against political opponents. Aptly dubbed "Skietgoed" or ammunition, his often ruthlessly effective journalism was used to snipe at political opponents. A favourite target was J. H. Hofmeyr who was expected to succeed Jan Smuts as Premier and whose support of racial equality was seen as foolish and a threat to White South Africans.
Botha was first elected to the national parliament from the town of George in the Western Cape, as a member of the National Party in 1948 at the beginning of the party's more than four decade tenure. Botha's relationship with the Coloured people of South Africa was ambivalent. As Assistant and Acting Secretary of the Cape National Party's special Committee of Inquiry into Coloured Affairs, he was party to the recommendations accepted by the 1945 NP Congress, which included advice to establish a Coloured Representatives Council. Despite this, he was at the forefront of those who ended Coloured representation in Parliament in 1956.
In October 1958 Dr H. F. Verwoerd appointed Botha as Deputy Minister of Internal Affairs, an office he held for three years. South Africa became a republic on 31 May 1961. In August of that year Prime Minister Verwoerd offered Botha a position in his cabinet as Minister of Community Development and Coloured Affairs. Verwoerd drew B. J. Vorster into the same cabinet as Minister of Justice. Both men were known to have formidable strongman qualities, mastery of the National Party (NP) machine, and the determination to pursue Verwoerd's segregationist policy of Apartheid without compromise.
Botha was the Minister responsible for the removal of Coloureds from District Six and he presided over other forced removal activities under the Group Areas Act. It is difficult to assess what he really thought of these events, but it is known that he argued with Cabinet colleagues over certain issues. Even though he almost fanatically believed in loyalty and discipline, he implemented their measures. This characteristic surfaced later in his disapproval of the airing of party disagreements in public, which caused him to censure leading Afrikaners like Piet Cillie, Schalk Pienaar, and Piet Marais for publicly suggesting it was time for reform.
During 1964, Botha became Minister of Public Works. In 1966, he was unanimously elected leader of the NP in the Cape Province and appointed as a member of the Board of Directors of Nasionale Pers Ltd. Botha was leader of the House of Assembly from 1976 until 1978. He was appointed Minister of Defence on 5 April 1966, a position he was to hold until 7 October 1980. This was a decisive experience that provided him with a militarist power base and worldview. At this time the emergence of the Soviet-backed Marxist MPLA in Angola was a cause of concern to the Ford administration in the United States as well as to the Pretoria government. The Americans invited South Africa to take part in a clandestine initiative to install a pro-Western government at Luanda. The Americans, Prime Minister John Vorster and his security chief, Hendrik van den Bergh, favoured a limited, covert operation but Botha and Chief of the Army, Magnus Malan, were convinced of Soviet designs on Africa. Believing that South Africa was the real Russian objective, Botha advocated a total invasion that would drive the MPLA from Luanda. They were overruled and in August 1975, South African troops entered southern Angola to supposedly protect the Kunene River Hydroelectric Scheme. The civil war that broke out escalated to include Cubans, South Africans, Russians, East Germans, Americans, and others who wished to secure the strategically positioned and mineral-rich territory.
The United States government was halted when Congress vetoed its request for funds to be given to the anti-MPLA troops. On 19 December 1975, the United States government suddenly withdrew its support. By this stage, the South African forces had advanced to the outskirts of the capital, Luanda. The South Africans, particularly Botha and Malan, were bitter about the humiliation of being obliged to withdraw from Angola. They believed that they had not been given enough time to prepare for the war, had been drawn into it by American (false) promises, and left without allies on the eve of victory. Meanwhile, with the South Africans withdrawal, Cubans and the MPLA moved up to the South West African (SWA, later Namibian) border where they shielded bands of armed SWAPO guerrillas, who were able to infiltrate and raid northern SWA.
Botha inherited this state of affairs in 1978. The military wasted no time in launching a series of aggressive cross-border incursions into Angola on SWAPO and Angolan forces, slowing down SWAPO raids into Namibia. These experiences, and the arms embargo South Africa was facing, spurred Botha into making South Africa self-sufficient in armament supplies. South Africa was soon ranked as the eleventh largest arms industry in the world with an annual turnover of R3 billion.
Botha was successful in forging the traditionally conservative military into a powerful multiracial, national armed force with a social and humanitarian support group to work among the Black population, which had become a major target of the border war. This did not affect the local population's support of SWAPO as a political party, but it did keep them relatively passive. During this time Botha not only played a leading role in South African decision-making about the Angolan War, but also took part in the negotiations with western powers over the future of SWA /Namibia.
Early in his years as defense minister, Botha gained a reputation for toughness, known as "kragdadigheid" in Afrikaans, as well as for efficient administration. These qualities pushed him to the fore when Prime Minister B. J. Vorster unexpectedly resigned in 1978. During this time Botha was also prominent as the Cape provincial leader of his party. Nevertheless, his elevation to the premiership on September 28, 1978, was to some degree unexpected and aided by a well-publicized scandal in the Department of Information. This fatally compromised the reputation of its minister, Connie Mulder, another serious contender for the position and then the National party's leader in the important Transvaal province. Thereafter, in a series of speeches, Botha seemed to try to direct the country into reformist paths and away from the racial "Apartheid" (separation) which had been an article of faith for the National party since 1948. The new prime minister told his fellow Whites that they would have to "adapt or die."
Botha's aims were the creation of a clean administration, law and order, constitutional reforms to include Coloureds and Indians (if only on paper), a gathering of South African states, and industrial decentralisation to improve the economic lot of the homelands. Linked with these aims was the thorny issue of how to concede some Black political participation in order to address the international criticism of Apartheid and rising resistance from the Black population and economic instability, in part due to sanctions. Although he did not admit that Apartheid was inhumane, he did see that it was costly and unproductive. The desire to locate Black people far away from the industrial centres went against his ambitions for the country's development. The principle of government by consensus was put forward as a practical way to introduce a programme of social and political restructuring, which would set the economy free and return it to sustained economic growth. It is doubtful whether Botha envisaged all the dramatic social and political adaptations that were to happen during his period in office. What is certain is that his idea of 'healthy power sharing' meant he would cling to 'group rights' as a means of maintaining White control, which he claimed was still in the best interests of South Africa.
When Botha turned his considerable energies to the task of re-ordering South African society, he confronted more daunting challenges than any of his National Party predecessors. He found himself handicapped by drought, a fall in the gold price, a depression, rising demands on the defence budget, the accelerating campaign of terrorism and sabotage by the African National Congress (ANC), and growing internal opposition to Apartheid. South Africa's defensive strategy involved cross-border activities and covert support for right-wing leaning resistance movements. Consequently, relations with its neighbours were strained. Moreover, deep divisions that had long afflicted South African society intensified the internal situation. To counteract the "total onslaught" against South Africa the Prime Minister developed the concept of 'total strategy' to cover many aspects of political, economic, military and security issues. He confronted South Africans with their first lesson in the process of radical re-education at Upington in 1979, and warned them that it was a case of "adapt or die".
Botha swiftly moved to restrict the power of bureaucrats who might short-circuit the process of change, but his promise to reduce over-government was only partially successful. Although the public service was reduced to twenty-two departments in April 1980, the changing social order demanded that there be more public servants, not less, and constitutional development inevitably resulted in an increase of functionaries.
Botha attempted to modify the Apartheid tenets of Afrikaner Nationalist ideology to introduce reforms, appearing to offer a better deal to the population. But he was contemplating the impossible: trying to find a way of sharing power without the White minority losing control. He set in motion the dismantling of some Apartheid legislation, thereby irreversibly dividing National Party support. Furthermore, he did not award Coloured and Indian moderates with real partnership in the new Tricameral Parliament. Nonetheless, his social, labour, and economic reforms were a significant development, and a gradual evolution toward non-racialism began to take place. A changing and increasingly volatile South African society led to the civil insurrection of 1984 and its repercussions around the country. Botha's response was the repression of activists and liberation movements under a state of emergency. The reform policy stagnated. Apartheid's policies drew increasing condemnation from the outside world, giving Botha little room to manoeuvre and less freedom to compromise. Apparently abandoning the idea of consensus, he took more and more power to himself in a style of government that came to be termed 'imperial'.
Botha's uncompromising policies greatly polarised his own party's views and eventually led to feuding within the National Party. In February 1989, he suffered a mild stroke and, caving in to cabinet pressure, resigned. The conservative-moderate Frederik W. de Klerk became state president later that year. Within months of the collapse of the Berlin Wall, de Klerk had announced the legalisation of anti-Apartheid groups – including the African National Congress – and the release of Nelson Mandela. De Klerk's rule saw the dismantling of the Apartheid system and negotiations that eventually led to South Africa's first racially inclusive democratic elections on April 27, 1994.
Botha was known by all as PW, and by some as Piet Wapen (Peter Weapon), the Axe Man or ‘Die Ou Krokodil'. He was feared for his abrasive personality, but his most vehement opponents respected his political nerve. He gained a powerful reputation as tough; an outstanding administrator, and hard worker, whose management style demanded much of his ministers. His anger, when provoked, was legendary. He was essentially a private person who seldom made comments about himself or his motivation. He kept aloof from all except his family and his personal staff. His unwillingness to be publicly expansive, and his hectoring media image clouded any real understanding of the man and his vision. It fell to him to face and manage (many would argue, mismanage) the process of change in this most challenging period of South Africa's history.
In 1998 he refused to testify before the Truth and Reconciliation Commission regarding Apartheid crimes and was held in contempt by the Commission. The Appeals Court subsequently overturned the charge.
Botha had three daughters and two sons from his first marriage with Anna Elizabeth Rossouw whom he married in 1943. After Elize's death in 1997, Botha married his British born wife Barbara Robertson whom he spent his last years with at their house 'Die Anker' near the Wilderness, Western Cape.
On 31 October 2006, Botha passed away at the age of 90 at his house 'Die Anker'. He was found dead in bed just after 20:00 pm by his wife Barbara. A day after Botha's death, the Director-General in the presidency office Rev Frank Chikane visited Botha's family to present an offer for a state funeral and other forms of assistance to this former state president. When responding to the state offer, Mrs Botha said her husband had not wanted a state funeral. "He was not a man that looked for honour and glory," she said.
Though his memorial service was opened for public attendance, his burial, was a private occassion. It took place on 8 November 2006 at Hoekwil, a settlement above Wilderness.