The reality TV star, 35, has made no secret of the fact she wants to return to her pre-baby weight - and has told fans that she is slowly getting there...
Alongside a photograph of weighing scales showing 120 pounds - around 8 stone 5 pounds - Kourtney wrote the message: "First day that I have seen this number in a while."
It's been three months since Kourtney gave birth to son Reign on 14 December - coincidentally the same date as her eldest child Mason's fifth birthday.
She and boyfriend Scott Disick also have a middle child, Penelope, who will be three in July.
Since welcoming baby Reign into the world, Kourtney has kept a low profile and has not shared any pictures of the newborn.
Instead, it seems the mummy-of-three has been concentrating on her children and leading a clean, healthy lifestyle.
Sharing a picture of a very yummy-looking pink smoothie over the weekend, Kourtney said: "My morning shake: banana, blueberries, chia seeds, bee pollen, almonds, rose water, ground flax seed meal, dates and ice. #allOrganic."
She also shared a picture of a slice of pizza with the caption: "I didn't, even though I wanted to."
Later, the famous sister shared a picture of herself with half-sister Kendall Jenner captioned "bad and it shows".
And both ladies look mighty fine to us!
Why is Kourtney famous? Find out more in the video below!
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