The announcement came in a statement from Bouteflika to the nation carried by the state news agency APS.
The 81-year-old president, who has been in power since 1999, suffered a stroke in 2013. He is rarely seen in public.
“In response to all pleas and calls … I declare today my candidacy for the presidential elections,” Bouteflika said.
On Saturday, Algeria’s ruling National Liberation Front (FLN) fielded Bouteflika as its contender for the April 18 vote.
In recent years, the opposition has raised questions about Bouteflika’s fitness to stay in power.
Bouteflika acknowledged his ill-health, but insisted he was still able to continue running the country’s affairs.
“Of course, I am no longer as physically strong as I was before. I haven’t hidden this one day from our people. However, the firm willpower to serve my country has never left me and will enable me to overcome difficulties related to illness,” he said.
Bouteflika also promised that if re-elected he will institute political, economic and social reforms.
“If you give me the honour of your precious trust next April, I will invite within this year all forces of the people to hold a national symposium, which will focus on reaching consensus on reforms,” he said, addressing Algerians.
He added the envisaged forum could propose constitutional changes, but he gave no details about what these could be.
Bouteflika’s top challengers are former Prime Minister Ali Benflis, the runner-up in the 2014 election; influential retired General Ali Ghediri; and the leader of a moderate Islamist party, Abderrazak Makri.
In recent years, Algeria’s finances have been hurt by the global drop in oil prices, prompting cuts in state subsidies.
At the time, his government contained pro-democracy protests in Algeria with promises of reform and pay raises, financed by the country’s revenues from oil and gas.
His re-election provided short-term stability for the FLN, the army and business tycoons, and postponed a potentially difficult succession.