Semisi Kioa Lafu Sika is a Tongan politician and Member of the Tongan Parliament. He is a member of the Democratic Party of the Friendly Islands.
Sika is a businessman who runs a takeaway shop and catering firm. He is a lonstanding supporter of the democratic movement in Tonga. In 2007 he was one of three people, including Human Rights and Democracy Movement leader Samuela 'Akilisi Pohiva, prosecuted over his leadership of a protest march in June 2006.
Sika was elected to Parliament in the seat of Tongatapu 2 in the 2010 elections.