Prior to the Spanish conquest, Colombia was inhabited by Chibcha, sub-Andean, and Caribbean peoples, all of whom lived in organized, agriculturally based communities. After the Spanish conquest, which began in 1525, the area of present-day Colombia formed the nucleus of New Granada (for colonial history, see New Granada). The struggle for independence was, as in all Spanish-American possessions, precipitated by the Napoleonic invasion of Spain. The revolution was, however, foreshadowed by the rising of the comuneros.

Prominent among the first revolutionary leaders was Antonio Nariño, who took part in the uprising at Bogotá on July 20, 1810. The revolution was to last nine years before the victory of Simón Bolívar at Boyacá (1819) secured the independence of Greater Colombia (Span., Gran Colombia). The new state Bolívar created included what is now Venezuela, Panama, and (after 1822) Ecuador, as well as Colombia. Cúcuta was chosen as capital. While Bolívar, who had been named president, headed campaigns in Ecuador and Peru, the vice president, Francisco de Paula Santander, administered the new nation. Political factions soon crystallized. Santander advocated a union of federal sovereign states, while Bolívar championed a centralized republic.

Although Bolívar's authority prevailed by and large in the constitutional assembly (1828), Greater Colombia soon fell apart. In 1830, Venezuela and Ecuador became separate nations. The remaining territory emerged as the republic of New Granada. Through the 19th cent. and into the 20th cent. political unrest and civil strife reappeared constantly. Strong parties developed along conservative and liberal lines; the conservatives favored centralism and participation by the church in government and education, and the liberals supported federalism, anticlericalism, and some measure of social legislation and fiscal reforms. Civil war frequently erupted between the factions. During the 19th and early 20th cent. three statesmen stand out—Tomás Cipriano de Mosquera, Rafael Núñez, and Rafael Reyes. While Mosquera was president, a treaty was concluded (1846) granting the United States transit rights across the Isthmus of Panama.

A new constitution in 1858 created a confederation of nine states called Granadina. Three years later (1861) under Mosquera, the country's name was changed to the United States of New Granada and in 1863 to the United States of Colombia. The antifederalist revolution of 1885 led one year later, during the presidency of Núñez, to the formation of the republic of Colombia and enactment of a conservative constitution. In 1899, five years after Núñez's death, civil war of unprecedented violence broke out and raged for three years. As many as 100,000 people were killed before the Conservatives emerged victorious. Another humiliation occurred when, after the United States had acquired the right to complete the Panama Canal (although the agreement was later rejected by the Colombian congress), the republic of Panama declared and, aided by the United States, achieved its independence from Colombia (1903).

During the semidictatorial administration (1904–9) of Reyes, internal order was restored and the country's trade and productivity were vigorously expanded. Reyes, nevertheless, had to resign because of discontent over his handling of the Panama issue. Soon afterward Colombia recognized (1914) Panama's independence in exchange for rights in the Canal Zone and the payment of an indemnity from the United States.

For the next four decades political life remained fairly peaceful, although there was economic and social unrest in the 1920s and 1930s. Colombia settled (1917) its boundary disputes with Ecuador, and in 1934 a border clash with Peru over the town of Leticia was settled by the League of Nations in Colombia's favor. Under the leadership of the liberals Olaya Herrera (1930–34), Alfonso López (1934–38), and Eduardo Santos (1938–42), wide-ranging reforms were enacted. Colombia participated in World War II on the Allied side. During the war years, internal divisions worsened. The Liberals split and in the 1946 elections presented two candidates, enabling the Conservatives to win.

In 1948, while an Inter-American Conference was being held in Bogotá, the leftist Liberal leader Jorge Eliécer Gaitán, under whom the party had reunited, was assassinated, precipitating violent riots and acts of vandalism. The death of Gaitán exacerbated the enmity between social groups and plunged the country into a decade of civil strife, martial law, and violent rule that cost hundreds of thousands of lives. Political violence turned into sheer criminality (la violencia), particularly in rural areas. An archconservative dictator, Laureano Gómez, took power in 1950, when the Liberals put forward no candidate. In 1953, Gómez was ousted by a coup led by Gustavo Rojas Pinilla, the head of the armed forces. Repressive measures continued, fiscal reforms failed, the country was plunged into debt, and Rojas Pinilla became implicated in scandalously corrupt schemes.

A military junta, backed by Liberals and Conservatives alike, ousted Rojas Pinilla in 1957. The following year Alberto Lleras Camargo became president, elected under the National Front coalition agreement. The National Front presidential candidate of 1970, Misael Pastrana Borrero, won very narrowly over Rojas Pinilla, who returned to politics as the champion of the underprivileged. Colombia's economy began to recover from the setbacks of the early 1970s as economic diversification and incentives to lure foreign capital into the country were initiated. However, a high inflation rate continued to impede economic growth. In 1974 the Liberal party candidate Alfonso López Michelsen won the first presidential election following the end of the National Front.

Throughout the 1970s and 80s, Colombia's illegal drug trade grew steadily, as the drug cartels amassed huge amounts of money, weapons, and influence. The 1970s also saw the growth of such leftist rebel groups as the May 19th Movement (M-19), the Revolutionary Armed Forces of Colombia (FARC), and the National Liberation Army (ELN). The violence continued, and many journalists and government officials were killed. The 1980s saw the rise of right-wing paramilitary groups, which were organized to oppose leftist rebels but also attacked on civilians. The guerrillas of the left and right both eventually became involved in the drug trade, which provided a ready source of funding.

In 1986, Virgilio Barco Vargas, of the Liberal party, was elected president; he was succeeded in 1990 by César Gaviria Trujillo, also a Liberal. In 1990 a Constitutional Assembly, which included members of the M-19 group, was elected to draft a new constitution; the document, which came into force on July 5, 1991, included protection for human rights and established citizens' rights to social security and health care. Liberal Ernesto Samper Pizano was elected president in 1994 and, though he appeared to make efforts to combat drug trafficking, he was accused of having accepted money from the Cali cocaine "cartel" for his election campaign. He was cleared of all charges (1996) by the Congress, but his administration was marked by charges of corruption and mismanagement.

The notorious Medellín drug cartel was broken in 1993, and the Cali cartel was later undermined by arrests of key leaders. Drug traffickers continued to have significant wealth and power, however, and FARC and the ELN remain actived, perpetuating a condition of instability. Conservative Andrés Pastrana Arango, a former mayor of Bogotá and son of Misael Pastrana, was elected president in 1998. He pledged to work with both leftist rebels and right-wing paramilitary leaders in an attempt to end more than 30 years of conflict in the country.

In Nov., 1998, Pastrana ceded an area the size of Switzerland in S central Colombia to FARC's control as a goodwill gesture, but the rebels negotiated with the government only fitfully, continued to mount attacks, expanded coca production, and essentially established a parallel government in the region under their control. The government's energies also were diverted by a severe recession in 1999 and a major earthquake that hit W Colombia early in 1999, leaving over a thousand people dead. Ongoing negotiations with the rebels in 2000 and 2001 were marred by rebel attacks and kidnappings and fighting between rebels and paramilitaries for control of coca-growing areas in Colombia. As a result, popular disenchantment with Pastrana increased, even as he moved forward with his "Plan Colombia," a $7 billion social aid and antidrug program that included $1.3 billion in largely military aid from the United States.

In Feb., 2002, after FARC hijacked a airplane and kidnapped a senator, Pastrana ordered the military to attack rebel positions and reassert control over the rebel zone. FARC withdrew into the jungle and began attacks against the power grid, telecommunications facilities, and other aspects of Colombia's infrastructure, in an attempt to disrupt the lives of the largely urban population while avoiding a direct conflict with the military. In May, a hard-line rightist candidate, Álvaro Uribe Vélez, who promised to crack down on the leftist rebels, won the presidential election. Uribe, a former governor and senator who ran as an independent, declared a limited state of emergency, broadening the government's police powers, as part of his campaign against the rebels.

By the end of 2003, the government's increased use of its forces had decreased violence somewhat, but the rebels remained strong, if withdrawn into the countryside. Also, the economy improved, cocaine production—a source of rebel income—was reduced with American help, and some paramilitary forces agreed to begin disarming. Despite his resulting popularity, however, in November Uribe lost a referendum that would have increased his control over the government's budget and made other structural governmental changes; the national debt had risen to 50% of the GDP. Negotiations with the paramilitary forces continued into 2004, by which time drug traffickers had become predominant among the paramilitary leaders. Safe zones were established for paramilitaries while negotiations were ongoing, and late in the the demobilization of some paramilitaries began.

The Dec., 2004, kidnapping by bounty hunters in Venezuela of a FARC leader, who was then turned over to Colombian authorities, led to a brief crisis in Colombia's relations with Venezuela in early 2005. Colombia first denied any involvement in the incident, claiming the rebel was captured in a Colombian border town, but subsequently admitted a bounty had been paid. The dispute between the two nations was settled by Feb., 2005, when the nations' presidents met in Caracas, Venezuela.

In June the congress passed legislation designed to facilitate the disarming of paramilitary groups by shielding them from extradition and minimizing the penalties they might faced. The law was criticized for not requiring a complete cease-fire or disarmament by participating groups and for not assuring that criminal activities such as drug-trafficking would end, and it indeed subsequently appeared that some former paramilitaries continued to operate as organized crime groups and corrupt government officials. However, by mid-2006 some 31,000 paramilitary fighters were reported to have demobilized, and in Aug., 2006, Uribe ordered the arrest of a number of senior paramilitary leaders who had refused to surrender as required.

Meanwhile, the situation with respect to the leftist rebels, who continued to mount successful, if more limited, attacks, remained largely unchanged. Uribe also secured changes to the constitution permitting the popular president to run for a second consecutive term. The government began a new round of talks with the ELN in Dec., 2005, but the FARC, who remained responsible for the most significant attacks, rejected any negotiations with Uribe's government. Parties aligned with President Uribe secured a majority of seats in both houses of the congress in the Mar., 2006, elections, and Uribe himself won reelection in May. Talks with the ELN continued through 2006, but did not produce substantive results.

A supreme court investigation exposed paramilitary links to members of Colombia's congress and other politicians, with widespread links revealed in N Colombia; several members of the congress were arrested in late 2006 and 2007. The foreign minister resigned because her brother, a senator, was one of those arrested in Feb., 2007. In Mar., 2007, a leaked CIA report linked the chief of the army to paramilitary death squads that had operated in 2002; the general denied the charge. Testimony from a former paramilitary warlord in May accused the current vice president and defense minister, former government officials, and military leaders of ties to and support for the paramilitaries, who were used to fight drug cartels and leftist rebels. In May, 12 generals were forced to resign after revelations of illegal wiretaps on political leaders and government officials. Revelations about government and military ties to the paramilitaries, the rebels, and the drug dealers continued during the summer; in July, several senators, including Uribe's cousin, became the subject of an investigation into paramilitary links. In August, Venezuela's leftist president, Hugo Chávez, offered to act a mediator with the rebels. Although Chávez's efforts led to the release of some hostages in 2008, they also caused strained relations between the two nations in 2007.

In Mar., 2008, a Colombian raid on rebels encamped in Ecuador led to several days of tensions between Colombia and neighboring Ecuador and Venezuela, who mobilized forces to their borders. Colombia said computer files seized in the raid had evidence of ties between the rebels and its neighbors' governments. Colombia subsequently apologized for the raid, which the Organization of American states called a violation of Ecuadorian sovereignty and the OAS charter.