A chronology of key events:
1500s - Ottomans absorb part of Yemen into their empire but are expelled in the 1600s.
Sanaa is one of the world's oldest continuously-inhabited cities
- Population: 1.6 million
- Sanaa means 'fortified place'
1839 - Aden comes under British rule, and when the Suez Canal opens in 1869 serves as a major refuelling port.
1849 - Ottomans return to north, but later face revolt.
1918 - Ottoman empire dissolves, North Yemen gains independence and is ruled by Imam Yahya.
1948 - Yahya assassinated, but his son Ahmad beats off opponents of feudal rule and succeeds his father.
1962 - Imam Ahmad dies, succeeded by his son but army officers seize power, set up the Yemen Arab Republic, sparking civil war between royalists supported by Saudi Arabia and republicans backed by Egypt.South Yemen formed
1967 - Formation of People's Republic of Yemen, comprising Aden and former Protectorate of South Arabia.
1969 - Marxists take power in south, rename state People's Democratic Republic of Yemen and reorient economy, society and foreign policy towards Soviet bloc.
1971 - Thousands flee to north following crackdown on dissidents. Armed groups formed in bid to overthrow government.
1972 - Border clashes between two Yemens, ceasefire brokered by Arab League.
1978 - Ali Abdallah Saleh becomes president of North Yemen.
1979 - Fresh fighting between two Yemens. Renewed efforts to unite the two states.
1982 - Earthquake kills 3,000.
1986 - Thousands die in south in political rivalry. President Ali Nasser Muhammad flees the country and is later sentenced to death for treason. New government formed.North and south unite
1990 May - Two Yemens united as Republic of Yemen with Mr Saleh as president, as Soviet bloc implodes. Tension between former states endures.
1992 - Food price riots in major towns.
1993 April - Coalition government formed, made up of ruling parties of former north and south.
1993 August - Vice-President Ali Salim al-Baid withdraws to Aden, alleging that south is being marginalised and southerners are being attacked by northerners.Attempted split
1994 May - Saleh declares state of emergency and dismisses al-Baid and other southern government members following political deadlock and sporadic fighting. Former armies that failed to integrate square off on old border.
1994 May-July - Al-Baid declares independence of Democratic Republic of Yemen. Northern forces capture Aden, southern leaders flee abroad and are sentenced to death in absentia.
1995 - Yemen, Eritrea clash over disputed islands in Red Sea.Al-Qaeda attacks
2000 October - US naval vessel USS Cole damaged in al-Qaeda suicide attack in Aden. Seventeen US personnel killed.
2001 February - Violence in run-up to disputed municipal polls and referendum, which back extension to presidential term and powers.
2002 February - Yemen expels more than 100 foreign Islamic clerics in crackdown on al-Qaeda.
2002 October - Al-Qaeda attacks and badly damages oil supertanker MV Limburg in Gulf of Aden ,killing one and injuring 12 crew members and costing Yemen dear in lost port revenues.
2003 April - The 10 chief suspects in the bombing of the USS Cole escape from custody in Aden. Two are re-captured in 2004.Houthi insurgency
2004 June-August - Hundreds die as troops battle Shia insurgency led by Hussein al-Houthi in the north.
2004 August - Court sentences 15 men on terror charges, including bombing of Limburg tanker in 2002.
2004 September - Government says its forces have killed dissident cleric Hussein al-Houthi, the leader of a revolt in the north.
2005 March-April - More than 200 people are killed in a resurgence of fighting between government forces and supporters of the slain rebel cleric Hussein al-Houthi.
2005 May - President Saleh says the leader of the rebellion in the north has agreed to renounce the campaign in return for a pardon. Minor clashes continue.
2005 July - Police and witnesses say at least 36 people are killed across the country in clashes between police and demonstrators protesting about a cut in fuel subsidies.
2005 December - More than 60 people are killed when a landslide destroys a mountain village around 20km from Sanaa.
2006 March - More than 600 followers of slain Shia cleric Hussein al-Houthi who were captured following a rebellion he led in 2004 are released under an amnesty.
2006 September - President Saleh wins another term in elections.
2007 January-March - Scores are killed or wounded in clashes between security forces and al-Houthi rebels in the north.
2007 June - Rebel leader Abdul-Malik al-Houthi accepts a ceasefire.
2007 July - Suicide bomber attacks a tourist convoy killing eight Spaniards and two Yemenis in the province of Marib.
2007 August - Citizens banned from carrying firearms in Sanaa. Demonstrations without a permit are outlawed.
2007 October - Volcano erupts on the Red Sea island of Jabal al-Tair where Yemen has a military base.
2007 November - Clashes between Yemeni tribesmen and army personnel protecting a Ukrainian oil company leave 16 people dead in the south-eastern Shabwa province.
2008 January - Renewed clashes between security forces and rebels loyal to Abdul-Malik al-Houthi.
2008 April - Clashes with troops as southern Yemenis protest against alleged northern bias in state job allocation. One man killed.
2008 March-April - Series of bomb attacks on police, official, diplomatic, foreign business and tourism targets. US embassy evacuates all non-essential personnel.
2008 September - Attack on US embassy in Yemeni capital Sana'a kills 18 people, including six assailants. Six suspects arrested.
2008 October - President Saleh announces arrest of suspected Islamist militants allegedly linked to Israeli intelligence.Demands for reform
2008 November - Police fire warning shots at Common Forum opposition rally in Sanaa. Demonstrators demand electoral reform and fresh polls. At least five protesters and two police officers injured.
2009 February - Government announces release of 176 al-Qaeda suspects on condition of good behaviour.
Al-Qaeda in action
• 1992 December - Bombers hit hotel in Aden formerly used by US marines - first known al-Qaeda attack in Yemen.
• 2000 October - Suicide attack on destroyer USS Cole in Aden.
• 2002 October - French tanker Limburg (pictured) damaged by bomb-laden boat.
• 2007 July - 8 Spanish tourists, 2 local drivers killed by car bomb.
• 2008 September - 16 killed in car bombings outside US embassy.
• 2009 January - Saudi, Yemeni al-Qaeda branches merge to form al-Qaeda in the Arabian Peninsula (AQAP).
• 2009 August - AQAP bomber dies in failed bid to kill Saudi deputy interior minister.
• 2009 December - 'Underwear bomber' Umar Farouk Abdulmutallab tries to down US airliner in plot claimed by AQAP.
• 2010 October - Parcel bombs, thought to have been made by al-Qaeda and dispatched in Yemen, found on US-bound cargo planes.
• 2011 May - AQAP fighters take control of southern city of Zinjibar.
• 2011 September - Al-Qaeda-linked, US-born cleric Anwar al-Awlaki killed in US air raid.
• 2012 February - Suicide attack on presidential palace kills 26 Republican Guards on day that President Hadi is sworn in. AQAP claims responsibility.
• 2012 May - 96 soldiers are killed by suicide bomber in Sanaa. AQAP claims the attack.
• 2012 June - Army retakes Zinjibar from AQAP after month-long offensive.
2009 June - Nine foreigners are abducted in remote Saada region. The bodies of three are later found. The fate of the remaining six hostages remains unclear, though local rebels deny responsibility.
2009 August - The Yemeni army launches a fresh offensive against Shia rebels in the northern Saada province. Tens of thousands of people are displaced by the fighting.
2009 October - Clashes break out between the northern rebels and Saudi security forces along the two countries' common border. The rebels accuse Saudi Arabia of supporting the Yemeni government in attacks against them. The Saudi government denies this.
2009 November - Saudi Arabia says it has regained control of territory seized by Yemeni rebels in a cross-border incursion.
2009 December - Yemen-based branch of al-Qaeda claims it was behind failed attack on US airliner. The government calls on the West for more support to help it combat the al-Qaeda threat.
2010 January - President Saleh says government open to talks with Al-Qaeda militants, provided they renounce violence.
2010 February - Government signs ceasefire with northern rebels.
2010 March - Northern rebels release 178 captives after the government accuses the Shia Houthi group of failing to comply with the terms of the truce reached in February.
2010 September - Thousands flee government offensive against separatists in southern Shabwa province.
2010 October - Global terror alert after packages containing explosives originating in Yemen are intercepted on cargo planes bound for the US.
2010 December - Yemen says 3,000 soldiers killed in recent outbreak of fighting involving Houthi rebels.
2011 January - US Secretary of State Hillary Clinton visits to express "urgent concern" at al-Qaeda activities in Yemen.
Tunisian street protests which unseat President Ben Ali appear to encourage similar demonstrations in other countries, including Yemen.
President Saleh pledges not to extend his presidency in 2013 or to hand over to his son.
2011 March - Pro-reform demonstrations continue. Police snipers open fire on pro-democracy camp in Sanaa, killing more than 50 people.
Senior military figures including key general, Ali Mohsen al-Ahmar, declare their backing for protest movement. Several ministers and other senior regime figures also defect to protesters.
President Saleh says unrest risks plunging country into civil war. State of emergency is imposed.
2011 April - Unrest and violent government response continue. President Saleh vows to remain in office.
2011 May - Dozens die in clashes between troops and tribal fighters in Sanaa. Airport shuts and thousands flee the city.
2011 June - President Saleh is injured in a rocket attack and is flown to Saudi Arabia.
British and French forces prepare to evacuate foreigners in the event of a civil war.
2011 September - President Saleh returns home.
US-born al-Qaeda leader Anwar al-Awlaki is assassinated by US forces.
2011 October - Yemeni human rights activist Tawakul Karman wins Nobel Peace Prize, together with Ellen Johnson Sirleaf and Leymah Gbowee of Liberia.
UN Security Council passes resolution condemning violence, calls for transfer of power.Unity government
2011 November - President Saleh agrees to hand over power to his deputy, Abdrabbuh Mansour Hadi.
Unity government - including a prime minister from the opposition - is formed.
2012 January - President Saleh leaves country. Parliament grants him full immunity in the face of objections from thousands of street protesters.
2012 February - Abdrabbuh Mansour Hadi inaugurated as president after uncontested elections.
2012 May - International donors pledge more than $4bn in aid to Yemen to help improve infrastructure and security. Aid agencies warn that Yemen is on the brink of food crisis. The government is thought to have asked for some $10bn.
An al-Qaeda leader Fahd al-Quso in Yemen wanted over the 2000 bombing of the US warship USS Cole is killed in an unmanned drone attack.
2012 June - The army recaptures three al-Qaeda strongholds in the south - Shuqra, Zinjibar and Jaar.
2012 September - Defence Minister Muhammad Nasir Ahmad survives car bomb attack in Sanaa that kills 11 people, a day after local al-Qaeda deputy head Said al-Shihri is reportedly dead in the south.
2012 November - A Saudi diplomat and his bodyguard are shot dead in Sanaa. Security officials say the assailants, who opened fire on the diplomat's convoy, were dressed in police uniforms.National dialogue
2013 March - Delayed national dialogue conference begins with aim of drafting new constitution.
2013 April - Ahmed Ali Saleh, son of ex-president Saleh, is removed as head of Republican Guard.
2013 July - US intensifies drone strikes against al-Qaeda.
2013 August - Several foreign embassies shut temporarily over fears of attacks by al-Qaeda.
Houthi rebels - resurgent Zaidis
Northern rebels, known as Houthis or Ansar Allah (Partisans of God), adhere to a branch of Shia Islam known as Zaidism. Zaidis ruled North Yemen for almost 1,000 years until 1962. They took control of Sanaa in 2014
2013 December - The shooting of a tribal leader at a military checkpoint in the eastern province of Hadramawt sparks mass protests in the provincial capital Mukalla.
2014 January - National Dialogue Conference winds up after ten months of deliberation, agreeing a document on which the new constitution will be based.
2014 February - Presidential panel gives approval for Yemen to become a federation of six regions as part of its political transition.
2014 July - Tribesmen blow up the country's largest oil pipeline, disrupting supplies from the interior to a Red Sea export terminal.
2014 August - President Hadi sacks his cabinet and overturns a controversial fuel price rise following two weeks of anti-government protests in which Houthi rebels are heavily involved.
2014 September - Houthi rebels take control of the capital Sanaa. The UN brokers a peace deal according to which the Houthis agree to withdraw their fighters from cities they have seized once a new national unity government has been formed.
2015 January - The Houthis reject the draft of a new constitution proposed by the government. They seize state TV and clash with troops in the capital, in what the government called a coup attempt.
President Hadi and his government resign in protest at the takeover by Houthi rebels of the capital. He later flees to his native city of Aden and rescinds his resignation.
2015 February - Houthi rebels say that they are seizing power and that transitional five-member presidential council will replace President Hadi.
UN Security Council denounces Houthi move, demands they negotiate power-sharing agreement under Gulf Cooperation Council aegis.