Kim Kardashian flaunts a VERY tiny waist as she celebrates her nephew Mason Disick’s 13th birthday in LA

Kim Kardashian stole the show when she arrived at the epic 13th birthday celebration of Mason Disick, her sister Kourtney Kardashian’s eldest son, in Los Angeles on Saturday night.

The SKKN founder, 42, flaunted her shrinking waist in high-waisted black leather pants covered in glittering black jewels.

She styled the statement pants with an extremely cropped Up in Smoke Tour t-shirt that ended just below her bust.

Scene thief: Kim Kardashian stole the show when she arrived at the home of her sister Kourtney Kardashian’s eldest son, Mason Disick, at the epic 13th birthday celebration in Los Angeles on Saturday night

Kim’s pants came with a matching small purse that wasn’t big enough for her phone.

She accessorised her with an eye-catching diamond necklace as well as a silver cross pendant chain.

Her nails were painted a baby pink to match the color of her thick pout.

The mother-of-four rocked her signature warm brown smoky eye and her lashes were covered in mascara to create a dramatic, spider-like look.

Kim’s golden tresses fell in soft curls to her waist.

Besties: Kim messed around with her “momager” Kris Jenner, who looked chic in all black

Hell for leather: The SKKN founder, 42, flaunted her shrinking waist in high-waisted black leather trousers covered in glittery black jewels

She strutted around the venue in a pair of pointy boots before stopping by the party’s Van Leeuwen Ice Cream Truck for a treat.

Kim sported her “momager” Kris Jenner, who looked chic in all black.

Other family members in attendance were: Mason’s mother Kourtney Kardashian, Khloe Kardashian, Kendall Jenner, Kylie Jenner, Mason’s little sister Penelope and little brother Reign.

Scott Disick, who Kourtney split from in 2015 after nearly a decade together, was also in attendance to celebrate their son’s special day. The former couple also shares Penelope and Reign.

Tiny top: She styled the statement pants with an extremely cropped Up in Smoke Tour t-shirt that ended just below her bust

Coordination: Kim’s pants came with a matching small purse that wasn’t big enough to hold her phone

Glam: The mother-of-four rocked her signature warm smoky brown eye and her lashes were coated in mascara to create a dramatic, spider-like look. Kim’s golden tresses fell in soft curls to her waist

Other family members in attendance were: Mason’s mother Kourtney Kardashian, Khloe Kardashian, Kendall Jenner, Kylie Jenner, Mason’s little sister Penelope and little brother Reign

Days before the family soiree, Kim wrote a sweet birthday tribute to her firstborn nephew, Mason.

She took to Instagram Stories to upload a photo of the two back-to-back, proving that Mason had topped Kim’s 5ft 2in frame.

She wrote of the picture: “The day has come when you are taller [than] me now.’

Cool mom: Meanwhile, Mason’s mom, Kourtney Kardashian, looked the ‘cool mom’ through and through in an edgy all-black outfit that included a chic low-cut bodysuit that accentuated her toned midsection and ample bust size

Stylish sisters: Kylie Jenner and Kendall Jenner brought their fashion-a-game to town for Mason’s birthday party

Curvy: Khloe Kardashian dressed up for the celebrations by showing off her sensational curves in a skintight black bodysuit

Eldest: Mason – who turned 13 on December 14 – is the eldest child of Khloe’s sister Kourtney Kardashian, 43, and ex-boyfriend Scott Disick

In the photo, the proud aunt was wearing a gray jacquard Skims bathrobe with black sunglasses and a black backpack on her shoulders.

Mason also wore a backpack, gray sweatpants and a white t-shirt while wearing a sweatshirt.

The entrepreneur was spotted with the platinum blonde locks she’s been rocking all year and the youngster sported a shaggy mushroom haircut.

Birthday tribute: Days before the family soiree, Kim wrote a sweet birthday tribute to her firstborn nephew Mason. She took to Instagram Stories to upload a photo of the two back-to-back, proving that Mason had topped Kim’s 5ft 2in frame

Kim added in the post, “I just love who you are and I’m just so proud of you Mason. Welcome to your teenage years. Happy Birthday.’

Kourtney Kardashian and Scott Disick’s second son, Reign, is celebrating his birthday with his older brother.

The boys were both born on December 14 but are five years apart and Reign is now eight years old.

Her siblings, sister Penelope Scotland Disick, turned ten in July.

Flashback: Kim and Mason pictured together in a flashback photo