Najib faces opposition leader Mahathir Mohamad, who served 22 years as the country's leader before retiring in 2003 and has come back determined to topple the party he once led.
Mahathir, 92, breathed life into the pre-election period with a stunning return to frontline politics by joining forces with his arch-nemesis, former deputy prime minister Anwar Ibrahim, whom he once jailed for corruption and sodomy.
Mahathir and Anwar have put aside rivalry to focus on defeating frontrunner Najib and his United Malays National Organisation (UMNO) party, which forms the largest constituent in the ruling Barisan Nasional coalition.
Najib made the announcement at his office in the country's administrative capital of Putrajaya, shortly after noon, local time.
He announced that the king had assented to the dissolution, which will take effect on Saturday, April 7.
The country will have to go to the polls within 60 days of dissolution. The country's Election Commission will now decide dates for nomination of candidates, the length of the campaigning period and the date for elections.
Prior to dissolution, Najib's Barisan Nasional coalition held 131 of 222 parliamentary seats.
In the forthcoming elections, voters will cast ballots for Parliamentary seats, as well as on seats in state legislatures, which are expected to be dissolved in the coming days.
More about: Malaysia
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