16 May 2003 – Morocco: Al-Sirat al-Mustaqim conduct near-simultaneous explosive attacks at five locations in Casablanca killing 42 and injuring 100.
17 May – United States: Armed Forces Day.
18 May 1980 – Peru: Sendero Luminiso (Shining path) began terrorist operations.
18 May 2009 – Sri Lanka: Thiruvenkadam Velupillai Prabhakaran the founder and leader of the Liberation Tigers of Tamil Eelam (LTTE or Tamil Tigers) is killed in a fire fight with SASF forces.
20 May 1902 – Cuba: Cuba gains independence from the United States.
20 May 2002 – Middle East: Jihad Ahmed Jibril, who headed the Popular Front for the Liberation of Palestine – General Command (PFLP-GC) military wing and was in line to replace his father, Ahmad Jibril as leader of the group, was killed by a car bomb in Beirut, Lebanon.
21 May 2002 – Peru: Car bomb detonates outside US Embassy killing nine Peruvians; Shining Path suspected.
22 May 2001 – Philippines: ASG rebels raid beach resort on Samal Island Davao killing two and injuring three.
25 May 1946 – Jordon: Independence was granted from Great Britain and King Abdullah Ibn al-Hussein was installed as the reigning monarch.
25 May 2001 – Israel: HAMAS and PIJ detonate two bombs at a bus station on the anniversary of the Israeli pullout from Lebanon in 2000.
27 May 2009 – Pakistan: Attack on security facilities in Lahore using car bomb, grenades and small arms kills 30, injures more than 250; TTP claimed responsibility.
27 May 2017 – Ramadan: Ramadan 2017: First day of fasting on the 27/28 May 17.
28 May 1964 – The Palestine Liberation Organisation (PLO) was formed.
28 May 2009 – Pakistan: Second day of attacks this time in Peshawar, kills 30 including several policemen; no claim of responsibility.
29 May 1964 – Columbia: Founding of the Revolutionary Armed Forces of Columbia (FARC).
31 May 1910 – South Africa: Union of South Africa formed.
Dates are taken from the NCTC terrorist calendar and 361 Security Significant dates.