Pieter Willem Botha (12 January 1916 – 31 October 2006), commonly known as "P. W." and Die Groot Krokodil (Afrikaans for "The Big Crocodile"), was the prime minister of South Africa from 1978 to 1984 and the first executive state president from 1984 to 1989.

Botha was a long-time leader of South Africa's National Party and an advocate of the apartheid system although, while in power, he did make concessions towards human rights. He was also a staunch opponent of Communism. Early in 1998, when Botha refused to testify at the Mandela government's Truth and Reconciliation Commission, he was supported by the far right-wing Conservative Party in his refusal but was fined and given a suspended jail sentence later that year. Botha was not related to contemporary National Party politician Roelof Frederik "Pik" Botha, who served as South Africa's foreign minister.

Botha was born on the farm Telegraaf in the Paul Roux district of the Orange Free State, the son of Afrikaner parents. His father, also named Pieter, fought in a commando against the British in the Second Boer War (1899 – 1902). During the war his mother was interned in a British concentration camp. He initially attended the Paul Roux School and matriculated from Voortrekker Secondary School Bethlehem, South Africa. In 1934, P.W. Botha entered the Grey University College (now the University of the Free State) in Bloemfontein to study law, but left early at the age of 20 in order to pursue a career in politics. He began working for the National Party as a political organiser in the neighbouring Cape Province.

In the years leading to World War II, Botha joined the Ossewabrandwag, or Oxwagon Sentinel (OB), a right-wing Afrikaner nationalist group which was sympathetic to the German Nazi Party. However in later years, with Allied victory looming in Europe, Botha was critical of this national socialist movement, favouring Christian nationalism instead, and condemned the Ossewabrandwag, charging it with "interference" in national politics.

In 1943, Botha married Anna Elizabeth Rossouw (Elize), and the couple had two sons and three daughters.

Botha was first elected to the House of Assembly representing the seat of George in the southern Cape, in 1948 at the beginning of the National Party's tenure in power, which was to last more than 40 years. In 1958 Botha was appointed Deputy Minister of Internal Affairs by Hendrik Verwoerd. He was appointed defence minister by Prime Minister B.J. Vorster in 1966. When Vorster resigned in 1978, Botha was elected as his successor by Parliament.

Though generally considered a conservative, Botha was also seen as far more pragmatic than his predecessor. He was keen to promote constitutional reform, and hoped to implement a form of federal system in South Africa that would allow for greater "self-rule" for black homelands (or Bantustans), while still retaining the supremacy of a white central government.

On becoming Prime Minister, Botha initially retained the defence portfolio until October 1980, when he appointed chief of the South African Defence Force, General Magnus Malan, as defence minister. Botha pursued an ambitious military policy designed to increase South Africa's military capability. He sought to improve relations with the West – especially the United States – but with mixed results. He argued that the preservation of the apartheid government, though unpopular, was crucial to stemming the tide of African communism, which had made in-roads into neighbouring Angola and Mozambique after these two former Portuguese colonies obtained independence. As Prime Minister and later State President, his greatest parliamentary opponents were Harry Schwarz and Helen Suzman of the Progressive Federal Party.

In the 1970s he began a secret nuclear weapons program in collaboration with Israel, which culminated in the production of six nuclear bombs. He also remained steadfast in South Africa's administration of the neighbouring territory South-West Africa, particularly while there was a presence of Cuban troops in Angola to the north. Botha was responsible for introducing the notorious police counter insurgency unit, Koevoet. He was also instrumental in building the South African Defense Force's strength. Adding momentum to establishing units such as 32 Batalion. South African intervention in support of the rebel UNITA (Dr. Jonas Savimbi, a personal friend) movement in the Angolan Civil War continued until the late 1980s, terminating with the Tripartite Accord. To maintain the nation's military strength, a very strict draft was implemented to enforce compulsory military service for white South African men.

In 1983 Botha proposed a new constitution, which was then put to a vote of the white population. Though it did not implement a federal system, it created two new houses of parliament, one for Coloureds (House of Representatives) and one for Indians (House of Delegates), along with that for whites-only (House of Assembly). The new Tricameral Parliament theoretically had equal legislative powers but the laws each new house passed were effective solely in its own community. Control of the country was maintained by the white house. The plan included no chamber or system of representation for the black majority. Black South Africans were expected to exercise their political rights within the context of the Bantustans. Each Black ethno-linguistic group was allocated a 'homeland' which would initially be a semi-autonomous area. Bantustans were expected to gradually move towards a greater state of independence with sovereign nation status being the final goal. During Botha's tenure Ciskei, Bophutatswana and Venda all achieved nominal nationhood. These new countries set up within the borders of South Africa never gained international recognition.

The new constitution also changed the executive branch, abolishing the post of prime minister. Instead, the role of head of government would be combined with that of head of state to create a strong, executive presidency with expanded powers. The presidency and cabinet had sole jurisdiction over areas deemed to be of "national" responsibility, such as foreign policy and race relations. Though the new constitution was criticised by the black majority for failing to grant them any formal role in government, many international commentators praised it as a "first step" in what was assumed to be a series of reforms. In 1984, Botha was elected as the first state president of South Africa under the newly approved constitution. Implementing the presidential system was seen as a key step in consolidating Botha's personal power. In previous years he had succeeded in getting a number of strict laws that limited freedom of speech through parliament, and thus suppressed criticism of government decisions.

In many western countries, such as the United States, the United Kingdom (where the Anti-Apartheid Movement was based) and the Commonwealth there was much debate over the imposition of economic sanctions in order to weaken Botha and undermine the white regime. By the late 1980s – as foreign investment in South Africa declined – disinvestment began to have a serious effect on the nation's economy.

In some ways, Botha's application of the apartheid system was less repressive than that of his predecessors: interracial marriage – which had been banned – was legalized, and the constitutional prohibition on multiracial political parties was lifted. He also relaxed the Group Areas Act, which barred non-whites from living in certain areas. In 1983, constitutional reforms granted limited political rights to Coloureds (South Africans of mixed white and non-white ancestry) and Indians. Late in his term, he became the first South African government leader to authorize contacts with imprisoned ANC leader Nelson Mandela. However, on the central issue of ceding power to blacks, he would not budge. In the face of rising discontent and violence, he imposed greater security measures such as states of emergency and state-sponsored covert action against anti-apartheid activists. He also steadfastly refused to negotiate with the African National Congress. Typical of his rule was his 1985 "Crossing the Rubicon" speech, a policy address in which Botha was widely expected to announce new reforms. Instead, he refused to give in to pressure for concessions to the black population including the release of Nelson Mandela. His defiance of international opinion in this speech led to further isolation of the country, calls for economic sanctions, and a rapid decline in the value of the rand. The following year, when the United States introduced the Comprehensive Anti-Apartheid Act, Botha declared a nation-wide state of emergency.

Thousands were detained without trial during his presidency, while others were tortured and killed. The Truth and Reconciliation Commission found him responsible for gross violations of human rights. It also found that he had directly authorized 'unlawful activity which included killing.' However, he refused to apologize for apartheid. In a 2006 interview to mark his 90th birthday he suggested that he had no regrets about the way he had run the country. He denied, however, that he had ever considered Black South Africans to be in any way inferior to whites, but conceded that "some" whites did hold that view. He also claimed that the apartheid policies were inherited from the British colonial administration in the Eastern Cape and Natal Province, implying that he considered them something he and his government had followed by default.

President Botha's downfall can be directly attributed to decisions taken at the Ronald Reagan/Mikhail Gorbachev summit of the leaders of the United States and the Soviet Union in Moscow (29 May - 1 June 1988) that paved the way to resolving the problem of Namibia which, according to foreign minister Pik Botha, was destabilising the region and "seriously complicating" the major issue which South Africa itself would shortly have to face. Soviet military aid would cease and Cuban troops be withdrawn from Angola as soon as South Africa complied with UN Security Council Resolution 435 by relinquishing control of Namibia and allowing UN-supervised elections there. The Tripartite Agreement, which gave effect to the Reagan/Gorbachev summit decisions, was signed at UN headquarters in New York on 22 December 1988 by representatives of Angola, Cuba and South Africa.

On 18 January 1989, Botha (then aged 73) suffered a mild stroke which prevented him from attending a meeting with Namibian political leaders on 20 January 1989. Botha's place was taken by acting president, J. Christiaan Heunis. On 2 February 1989, Botha resigned as leader of the National Party (NP) anticipating his nominee - finance minister Barend du Plessis - would succeed him. Instead, the NP's parliamentary caucus selected as leader education minister F W de Klerk, who moved quickly to consolidate his position within the party. In March 1989, the NP elected de Klerk as state president but Botha refused to resign, saying in a television address that the constitution entitled him to remain in office until March 1990 and that he was even considering running for another five-year term. Following a series of acrimonious meetings in Cape Town, and five days after UNSCR 435 was implemented in Namibia on 1 April 1989, Botha and de Klerk reached a compromise: Botha would retire after the parliamentary elections in September, allowing de Klerk to take over as president. However, Botha resigned from the presidency abruptly on 14 August 1989 complaining that he had not been consulted by de Klerk over his scheduled visit to see president Kenneth Kaunda of Zambia:

"The ANC is enjoying the protection of president Kaunda and is planning insurgency activities against South Africa from Lusaka," Botha declared on nationwide television. He said he had asked the cabinet what reason he should give the public for abruptly leaving office. "They replied I could use my health as an excuse. To this, I replied that I am not prepared to leave on a lie. It is evident to me that after all these years of my best efforts for the National Party and for the government of this country, as well as the security of our country, I am being ignored by ministers serving in my cabinet."

De Klerk was sworn in as acting president on 15 August 1989 and the following month was nominated by the electoral college to succeed Botha in a five-year term as state president. 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 27 April 1994. In a statement on the death of former president P W Botha in 2006, de Klerk said:

"Personally, my relationship with P W Botha was often strained. I did not like his overbearing leadership style and was opposed to the intrusion of the State Security Council system into virtually every facet of government. After I became leader of the National Party in February 1989 I did my best to ensure that P W Botha would be able to end his term as president with full dignity and decorum. Unfortunately, this was not to be."

Botha and his wife Elize retired to their home, Die Anker, in the town of Wilderness, close to the city of George and located on the Indian Ocean coast of the Western Cape. His wife Elize died in 1997, and he later married Barbara Robertson, a legal secretary 25 years his junior, on 22 June 1998. Botha remained largely out of sight of the media and it was widely believed that he remained opposed to many of F W de Klerk's reforms.

Botha refused to testify at the new government's Truth and Reconciliation Commission for exposing apartheid-era crimes, which was chaired by his cultural and political nemesis, Archbishop Desmond Tutu. The TRC found that he had ordered the bombing of the South African Council of Churches headquarters in Johannesburg. In August 1998 he was fined and given a suspended jail sentence for his refusal to testify in relation to human rights violations and the violence sanctioned by the State Security Council (SSC) which he, as president until 1989, had directed. In June 1999 Botha successfully appealed to the High Court against his conviction and sentence. The Court found that the notice served on Botha to appear before the Commission was technically invalid.

Botha died of a heart attack at his home in Wilderness on 31 October 2006, aged 90.

His death was met with magnanimity by many of his former opponents. Former President Nelson Mandela was reported as saying "while to many Mr Botha will remain a symbol of apartheid, we also remember him for the steps he took to pave the way towards the eventual peacefully negotiated settlement in our country." President Thabo Mbeki announced that flags would be flown at half mast, to mark the death of a former head of state. The offer of a state funeral was declined by Botha's family, and a private funeral was held on 8 November in the town of George where Botha was buried. Mbeki, who had lost a brother, a son and a cousin during apartheid, attended the funeral and was even seen to shed a tear or two. The following day, pictures of this were printed on the front pages of most of the regional newspapers.