You need a visa to enter Sri Lanka. See Visas.
Foreign nationals, with the exception of media crews, no longer need permission from the Sri Lankan Ministry of Defence before travelling to the northern districts of Jaffna, Kilinochchi, Mannar, Mullaittivu and Vavuniya. Military activities are ongoing and you should obey orders from the security forces and signs warning of the danger from land-mines. See Local travel - North.
Political rallies in Sri Lanka have sometimes turned violent. You should avoid any political gatherings or rallies. See Political situation.
There is an underlying threat from terrorism. See Terrorism.
Most visits to Sri Lanka are trouble-free, but you should be aware of the risk of credit card fraud, road accidents, drownings and dengue fever which is transmitted by mosquito bites.
Sri Lanka can be affected by severe weather like tropical cyclones and monsoon rains. See Natural disasters.
Take out comprehensive travel and medical insurance before you travel.