A chronology of key events:
1945 - After World War II, Japanese occupation ends with Soviet troops occupying area north of the 38th parallel, and US troops in the south.
1948 - Republic of Korea proclaimed.
1950 - South declares independence, sparking North Korean invasion.
1953 - Armistice ends Korean War, which has cost two million lives.
1950s - South sustained by crucial US military, economic and political support.
1960 - President Syngman Ree steps down after student protests against electoral fraud. New constitution forms Second Republic, but political freedom remains limited.
1961 - Military coup puts General Park Chung-hee in power.
1963 - General Park restores some political freedom and proclaims Third Republic. Major programme of industrial development begins.
1972 - Martial law. Park increases his powers with constitutional changes.
After secret North-South talks, both sides seek to develop dialogue aimed at unification.
1979 - Park assassinated. General Chun Doo-hwan seizes power the following year.
1980 - Martial law declared after student demonstrations. In the city of Gwangju army kills at least 200 people. Fifth republic and new constitution.
1981 - Chun indirectly elected to a seven year term. Martial law ends, but government continues to have strong powers to prevent dissent.
1986 - Constitution is changed to allow direct election of the president.
Return to democracy
1980s - Increasing shift towards high-tech and computer industry.
1987 - President Chun pushed out of office by student unrest and international pressure in the build-up to the Sixth Constitution. General Roh Tae-woo succeeds President Chun, grants greater degree of political liberalisation and launches anti-corruption drive.
1988 - Olympic games in Seoul. First free parliamentary elections.
1991 - North and South Korea join United Nations.
1993 - President Roh succeeded by Kim Young Sam, a former opponent of the regime and the first freely-elected civilian president.
1996 - South Korea admitted to Organisation for Economic Cooperation and Development.
1998 - Kim Dae-jung sworn in as president and pursues "sunshine policy" of offering unconditional economic and humanitarian aid to North Korea.
2000 June - Summit in Pyongyang between Kim Jong-il and South Korean President Kim Dae-jung. North stops propaganda broadcasts against South.
2000 August - Border liaison offices re-open at truce village of Panmunjom. South Korea gives amnesty to more than 3,500 prisoners. One hundred North Koreans meet their relatives in the South in a highly-charged, emotional reunion. Kim Dae-jung awarded Nobel Peace Prize.
2001 - Opening of Incheon International Airport, built on tidal land off port of Incheon.
2002 March - Group of 25 North Koreans defect to South Korea through Spanish embassy in Beijing, highlighting plight of tens of thousands hiding in China after fleeing famine, repression in North.
2002 June - Battle between South Korean and North Korean naval vessels along their disputed sea border leaves four South Koreans dead and 19 wounded. Thirty North Koreans are thought to have been killed.
2002 December - Roh Moo-hyun, from governing Millennium Democratic Party, wins closely-fought presidential elections.
2003 October - Biggest mass crossing of demilitarised zone since Korean War: Hundreds of South Koreans travel to Pyongyang for opening of gymnasium funded by South's Hyundai conglomerate.
2004 February - Parliament approves controversial dispatch of 3,000 troops to Iraq.
2004 June - US proposes to cut its troop presence by a third. Opposition raises security fears over the plan.
2005 June - Kim Woo-choong, the fugitive former head of Daewoo, returns and is arrested for his role in the industrial giant's $70bn-plus collapse. In May 2006 he is sentenced to 10 years in jail.
2005 December - South Koreans are shocked by revelations that cloning scientist and national hero Dr Hwang Woo-suk faked landmark research on stem cell research. 2006 October - Foreign Minister Ban Ki-moon is appointed as the UN's new secretary-general. He takes office in January 2007.
2007 February - South and North Korea agree to restart high-level talks suspended since July 2006 in wake of North's nuclear test.
Head of the largest South Korean car maker, Hyundai, is jailed for three years for embezzlement.
2007 April - South Korea and the US agree on a free-trade deal after 10 months of talks, although US Congress only ratifies it in 2011.
2007 May - Passenger trains cross the North-South border for the first time in 56 years.
2007 December - Conservative Lee Myung-bak wins landslide victory in presidential election.
2008 February - The country's greatest cultural treasure, the Namdaemun Gate, is destroyed by fire.
2008 October - Government announces $130bn financial rescue package to shore up banking system and stabilise markets amis global financial crisis.
2009 January - North Korea says it is scrapping all military and political deals with the South.
2009 August - Former South Korean president Kim Dae-jung dies; North Korea sends a senior delegation to Seoul to pay its respects.
2009 October - North Korea expresses "regret" for unleashing dam water that drowned six campers downstream in South Korea in September. The two sides hold talks aimed at preventing flooding on the Imjin River which spans their militarised border.
2009 November - South and North Korean warships exchange fire across a disputed sea border, and again in January.
2010 January - North accepts an offer of food aid from South, the first such aid in two years.
Sinking of warship
2010 May - South Korea breaks off all trade with the North after naval ship Cheonan was sunk by a North Korean torpedo in March. Pyongyang describes the findings as a "fabrication" and cuts all diplomatic ties with Seoul.
2010 November - Cross-border clash near disputed maritime border results in death of two South Korean marines. South Korea places its military on highest non-wartime alert after shells land on Yeonpyeong island. Further exchange of fire in August.
2012 July - South Korea begins move of most ministries to "mini capital" at Sejong City, 120km south of Seoul. Key ministries will remain in Seoul.
2012 August - Lee Myung-bak becomes first president to visit the Liancourt Rocks, which Japan also claims. Tokyo recalls its ambassador in protest.
2012 October - South Korea strikes deal with the US to almost triple the range of its ballistic missile system to 800km as a response to North Korea's test of a long-range rocket in April.
2012 December - South Korea elects its first female president, Park Geun-hye, of the conservative Saenuri party. She takes office in February.
New spike in tensions
2013 January - South Korea launches a satellite into orbit for the first time using a rocket launched from its own soil. Comes weeks after a North Korean rocket placed a satellite in orbit.
2013 March - South Korea accuses North of a cyber-attack that temporarily shuts down the computer systems at banks and broadcasters.
2013 September - North and South Korea reopen Kaesong joint industrial complex and hotline.
2013 December - South Korea announces expansion of air defence zone, two weeks after China unilaterally announced its own extended air defence zone in East China Sea to include disputed Socotra Rock.
2014 March - North and South Korea exchange fire into sea across the disputed western maritime border during largest South-US military training exercise in region for 20 years.
2014 April - Sewol ferry sinks off west coast, killing at least 281 people, mainly high-school students.
2014 October - North and South Korea engage in rare exchange fire across their land border as South Korean activists launch balloons containing leaflets condemning North Korean leader Kim Jong-un. Gun fire also exchanged when Northern patrol ship crossed disputed western maritime border.
US and South Korea again postpone transfer of control over troops in South in event of war with North, citing "intensifying threat" from Pyongyang. Transfer due in 2012, and delayed until 2015. No new date set.
2014 December - Constitutional Court bans left-wing Unified Progressive Party, accused of being pro-North Korean.
President Park calls for cyber security at key facilities to be strengthened after data on its nuclear reactors is leaked.
2015 March - North Korea fires short-range surface-to-air missiles into the sea in an apparent show of force against annual military drills between South Korea and the United States.
2015 November-December - Mass protests in Seoul against government's economic policy and insistence on schools' using state-approved history books.
2016 October - President Park Geun-Hye is embroiled in a political crisis over revelations that she allowed a personal friend, with no government position, to meddle in affairs of state. She is later impeached.
2016 December - South Korea's military says its cyber command came under attack by North Korean hackers.
2017 May - The centre-left candidate Moon Jae-in is elected president in a landslide, and pledges to solve the North Korean crisis by diplomatic means.
2018 January - North and South Korea agree to march under the same flag at next month's Winter Olympics in South Korea in a thaw in relations.
2018 April - Kim Jong-un becomes first North Korean leader to enter the South when he meets President Moon Jae-in for talks at the Panmunjom border crossing. They agree to end hostile actions and work towards reducing nuclear arms on the peninsula.