Mr Yar'Adua will be laid to rest on Thursday in his home state of Katsina
Fifty-eight-year-old Nigerian President Umaru Yar'Adua died at his presidential villa on Wednesday, state TV has announced.
Mr Yar'Adua, who became president in 2007, had been ill for some time.
BBC News website readers have been sending their reaction.
Even though the death of President Yar'Adua didn't come as a shock, I am still trying to come to terms with his demise. It feels like the death of a close relation. He was such a gentleman. May his gentle soul rest in eternal peace.
Olojede Titilola, Lagos, Nigeria
I believe that the official announcement of the death of the president will put an end to playing politics with his health. The acting president will now be allowed to focus on leading the nation forward.
Sada Wiseone, Calabar, Cross River State, Nigeria
We Nigerians have been hearing all sorts of rumours about our president's health for some time, but if he really is dead I pray that our good lord will grant him eternal rest.
Damian Chinedu, Anambra, Nigeria
Nigeria is a great nation with great people but power monopoly is wreaking havoc on our economy. Let Yar'Adua's death be a lesson to all.
It's a national tragedy, although it's a shame most Nigerians won't give a hoot about it. I just hope that Goodluck Jonathan gets in there and does the necessary reforms, irrespective of cultural background and ethnicity. Nigeria needs a leader that won't succumb to the selfish desires of the self-acclaimed godfathers, a leader who would give back to the people what they truly deserve. It has already begun with the electorate, it should expand to all other sectors. This is the time for our development, which will begin from the grassroots.
Jude Nwulu, Baltimore, USA
With a deep sense of loss, we Nigerians in the diaspora mourn the death of our president, Mr Yar'Adua.
Kingsley Ikechi, Rock Springs, USA
He was a good man, a man that meant well for this nation but could not achieve his aims because of his ill health. May his gentle soul rest in perfect peace.
Matthew Olarewaju, Osogbo, Nigeria
President Yar'Adua was a good man. His determination to solve the Niger Delta problem proved as much. But his persistent ill health was a problem. May his gentle soul rest in peace.
Comrade Etiowo, Enugu, Nigeria
It is really a sad time for our country. It is such a great loss. The man really portrayed gentleness. The grief will, I'm sure, have a lasting impact. God bless Nigeria because we will really need that blessing.
John Adams, Lagos, Nigeria
Although he had a short time as president, Yar'Adua is still the best president Nigeria has ever produced. His sincerity, selflessness and commitment will forever be remembered. RIP Mr President, we love you.
Aka Emeka, Enugu, Nigeria
He was a good man. But his ill health and the politics of swearing in Goodluck Jonathan as acting president almost turned Nigeria on its head. Now we must focus on the issue of who will be vice president to Jonathan. That might heat up the political system again.
Itemoagbo John Aigboje, Lagos, Nigeria
For all that Mr Yar'Adua has gone through, especially since November, I think that his passing is better than him having to endure any more suffering. I wish he had given way to governance and focused on his health. Maybe, he would have saved both Nigeria and himself.
Godwyns Onwuchekwa, London, UK
He should have willingly and fully surrendered power to Goodluck Jonathan. He knew he was not capable of leading any more. May his soul rest in peace.
Kemka Ihenaka, Texas, US
Though he had been on his sick bed for some months now, I find it very difficult to believe that President Umaru Musa Yar'Adua is no more. He will forever be remembered for his fairness. Nigerians will miss him. May his gentle soul rest in perfect peace.
Afeni Babajide, Iyin Ekiti, Nigeria
It's a pity he's dead but the country has to move on. At least we now know we have a way forward.
Ademola Adeboyejo, Edo State, Nigeria
I feel it is time for him to rest because he has been sick for a long time. He should have resigned power some time ago.
Jubril Oyewole, Lagos, Nigeria
Our president was a man of proven integrity and with good and bright intentions for Nigeria and the world at large. I pray that the new president will consolidate his vision. May his soul rest in peace.
David Udiminue, Uyo, Nigeria
This is one of the most turbulent periods in Nigeria's political history. Yar'Adua is now dead. May God give us the fortitude to bear the loss. Adieu Mr President. Rest in peace until we meet again.
Ekene Ozibo, Abuja, Nigeria
He was Nigeria's best-loved president and our hearts are heavy. Rest in peace Umaru.
Apeku, Makurdi, Nigeria
It is shocking and sad news, may God give his family the fortitude to bear this irreparable loss.
Engr Balogun Taye, Ondo State, Nigeria
It is sad news. For now everything is calm. May his soul rest in peace.
Oluwole, Lagos, Nigeria
It is a loss to his family no doubt, but the vast majority of Nigerians would be indifferent to the news of his passing because the people close to him mishandled his illness and succeeded in alienating him from any good will he may have otherwise enjoyed. Now that he's dead, Goodluck Jonathan will have to be sworn in as the substantive president. The moral of all this is that our country is bigger than any one individual. May his soul rest in peace.
Supo Adebayo, Mississauga, Ontario, Canada
The situation is calm. Not many are people aware yet. I just got the information. Our former president did and meant well for the nation. He will be greatly missed by all Nigerians. May the Lord comfort his family.
Rev. EA Fidoro, Warri, Nigeria