The first pic of Kourtney Kardashian's little baby boy.

And we love the name.

Kourtney Kardashian welcomed her third child, a baby boy, a week ago today.

And she just revealed the baby’s name with this adorable instagram snap.

Via Kourtney Kardashian Instagram.

She captioned the image with:

"Madly in love with my little Reign Aston Disick."

The Us Weekly said that the 35-year-old gave birth on Sunday, Dec 14, which was also her son Mason Disick's fifth birthday.

"Happy birthday to the coolest little boy in the entire world. You teach me so much every single day and changed my universe the second I met you. You have taught me what life is all about and I am truly blessed and honored to be your mommy." Via Kourtney Kardashian's Instagram.

Now there's an excuse to cut back on the lavish birthday parties!

The reality star and her partner Scott Disick are already parents to Mason, 5 and Penelope, 2.

Mason and Penelope. Via Kourtney Kardashian Instagram.

Kourtney recently posed for DuJour Magazine.

Kourtney Kardashian posing nude with her baby bump.

No word yet on the name of the bub but we'll update with more news as it comes.

You can check out her best maternity style moments in the gallery below...

Want more? Try these:

Pregnant Kourtney Kardashian pulls a Kim and strips down for a nude photo shoot.

Kourtney Kardashian, maternity style queen.