The 'Girl On Fire' singer welcomed her second child with husband Swiss Beatz three days ago on Saturday 27 December.
Announcing her baby joy, Alicia shared a cute snap of her newborn's footprints, revealing his name, weight and time of birth.
Her baby boy arrived in the early hours on Saturday morning, weighing in at 6lbs 5oz.
Alongside her photo, she wrote: "The joy of joy is joy!! It's a boy!! We are so grateful!! #blessings!!"
On seeing her post, many of Alicia's fans were quick to congratulate the star on her new arrival.
One user commented: "Congratulations! Much love and happiness to all of you!"
While another said: "Congratulations with the new addition to your family. God Bless little Genesis."
Alicia and Swiss - her husband of four years - first announced they were expecting another child together on their wedding anniversary in July.
Soon after, Alicia revealed she was due to give birth on New Years Eve, but instead Genesis was born five days early.
The couple are already parents to four-year-old Egypt, who has been looking forward to having another sibling.
Speaking before the birth of her second son, Alicia said Egypt was "so ready" to be a big brother.
"Are you kidding?! He's not going to be the baby anymore. He's so ready," she claimed.
Reveal is now on Google Plus! Join us here for the latest pictures, fashion and celebrity news!
See other celebrities who have given birth in 2014 in our gallery below:
Copyright: Rex Features WENN/Matthew Taylor/Daniel Deme/Josiah True/Matthre Taylor/Joe