October 21, 2017 (Saturday)
Armed conflicts and attacks
- War in Somalia
- 14 October 2017 Mogadishu bombings
- The death toll in Somalia's deadliest terror attack rises up to 358, making it the fifth-deadliest terror attack worldwide. (Irish Independent)
- 14 October 2017 Mogadishu bombings
- Insurgency in the Sahel
- War in Afghanistan (2001–2021)
- A suicide bomber kills at least 15 people in Kabul. (CNN)
Disasters and accidents
- 2017–18 UK and Ireland windstorm season
- Storm Brian, the third windstorm of the season, causes severe flash flooding in Ireland and coastal flooding in parts of England and Wales, although disruption is not as severe as initially expected. (BBC)
- Helicopter accidents and incidents
- A helicopter carrying five people crashes into Kenya's Lake Nakuru. (Capital FM)
- Landslides in Malaysia
Health and medicine
- 2017 Madagascar plague outbreak
- The death toll from an outbreak of plague in Madagascar nears 100. So far, there have been 911 cases recorded. (Reuters via ABC News Australia)
Politics and elections
- Czech legislative election, 2017
- The ANO movement of billionaire Andrej Babiš wins a sizeable plurality of seats in the Chamber of Deputies, but falls short of a majority. (The New York Times)
- The three next largest parties become the Civic Democratic Party, the Czech Pirate Party, and the far-right Freedom and Direct Democracy, as support for the governing Czech Social Democratic Party collapses. (DW)
- Argentine legislative election, 2017; Santiago Maldonado case
- Parties in Argentina halt their election campaigns due to the appearance of a body thought to be Santiago Maldonado, an indigenous rights activist who disappeared at the beginning of August 2017. (The Guardian)
- 2017 Iraqi–Kurdish conflict
- Iraqi forces complete the takeover of Kirkuk Governorate, which is outside the autonomous zone accorded by the Constitution of Iraq. Grand Ayatollah Ali al-Sistani calls for the state to protect Kurds in northern Iraq. (Reuters)
- 2017 Spanish constitutional crisis
- The Prime Minister of Spain, Mariano Rajoy, activates Article 155 of the Constitution of Spain. This will put Catalonia under the direct control of the central government, removing the regional government and completely limit the power of the Parliament of Catalonia. The regional police and media will also be under its control. (The New York Times)