With the ruling, Huda al-Ajmi will become the first woman to go to jail in Kuwait over the use of Twitter after receiving the longest sentence for online dissent in the Persian Gulf state.
She was convicted of insulting Emir Sheikh Sabah al-Ahmad al-Sabah, calling for the overthrow of the regime and misusing her cellphone, according to a copy of the lower court ruling. The director of the Kuwait Society for Human Rights, Mohammad al-Humaidi, confirmed the verdict on Twitter, the popular micro-blogging website. Ajmi was handed five years for each of the first two charges and one year for the third, becoming the first woman to be sent to jail over Twitter use.
The sentence is also the harshest for an online activist in Kuwait since the government began a clampdown on opposition tweeters in October last year.
Previously, Kuwaiti courts had sentenced at least two female activists to lighter jail terms but suspended the implementation.
Ajmi has categorically denied the charges.
She will have to start serving the prison term immediately until the appeals court starts hearing the case and decides whether she should remain in jail, said the verdict.
Under Kuwaiti law, Ajmi can challenge the ruling at the appeals court and later to the supreme court.
Ajmi is the latest in a growing list of tweeters and former-opposition MPs to face trial or receive jail terms for allegedly insulting the emir.
Opposition youth activist Rashed al-Enezi has been in jail since January for tweets deemed offensive to the emir. He is serving a 20-month prison term and is on trial in two other similar cases.
In April, the lower court sentenced opposition leader and former MP Mussallam al-Barrak to five years in prison for comments he made at a public rally in October deemed offensive to the emir.
The ruling sparked street protests by opposition activists, and was widely condemned by international human rights groups.
Criticising the emir in Kuwait is considered a state security offence and carries a maximum jail sentence of five years.
Kuwait has seen many opposition-led demonstrations against changes to the electoral law, which opposition groups say allowed the government to influence election results and elect a rubber-stamp assembly.
The country's constitutional court, whose rulings are final, is scheduled to issue a crucial ruling on June 16 on whether the controversial changes, ordered by the emir, were in line with the constitution.