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

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

The 42-year-old SKKN founder flaunted her dwindling waist in a pair of black leather high-waisted pants covered in shiny black jewels.

She paired the statement pants with an ultra-cropped Up in Smoke Tour T-shirt that hit just below her bust.

Scene stealer: Kim Kardashian stole the show when she arrived at the epic 13th birthday party for her sister Kourtney Kardashian's eldest son, Mason Disick, in Los Angeles on Saturday night.

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

Kim’s pants came with a matching tiny bag that wasn’t big enough to fit her cell phone.

She accessorized with a striking diamond choker necklace, as well as a silver cross pendant chain.

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

The mother-of-four sported her signature warm brown smoky eyes and her lashes were coated in mascara to create a dramatic, spidery look.

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

Besties: Kim hung out with her 'momager' Kris Jenner, who looked chic in black

Besties: Kim hung out with her ‘momager’ Kris Jenner, who looked chic in black

Hell for leather: The SKKN founder, 42, flaunted her dwindling waist in a pair of black leather high-waisted pants covered in shiny black jewels.

The sides of the legs and around the waist had most of the crystal detailing.

Hell for leather: The SKKN founder, 42, flaunted her dwindling waist in a pair of black leather high-waisted pants covered in shiny black jewels.

She paraded around the venue in a pair of pointy boots before stopping at the party’s Van Leeuwen ice cream truck to receive a treat.

Kim hung out with her momager Kris Jenner, who looked elegant in all black.

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

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

Tiny Top: She paired the statement pants with an ultra-cropped Up in Smoke Tour T-shirt that stopped just below her bust.

Tiny Top: She paired the statement pants with an ultra-cropped Up in Smoke Tour T-shirt that stopped just below her bust.

Coordination: Kim's pants came with a matching small bag that wasn't big enough to hold her cell phone

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

Glamour: The mom of four sported her signature warm brown smoky eye and her lashes were coated in mascara for a dramatic, spidery look

Golden girl: Kim's golden locks fell in soft curls to her waist

Glamour: The mom of four sported her signature warm brown smoky eye and her lashes were coated in mascara for a dramatic, spidery look Kim’s golden locks fell in soft curls to her waist.

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

Other family members in attendance included: 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 penned a sweet birthday tribute to her firstborn nephew Mason.

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

She wrote over the image, ‘The day has come when you are taller [than] I now.’

Cool mom: Meanwhile, Mason's mom, Kourtney Kardashian, looked like the 'cool mom' in an edgy all-black outfit that included a sleek cropped bodysuit that highlighted her toned tummy and ample bust

Cool mom: Meanwhile, Mason's mom, Kourtney Kardashian, looked like the 'cool mom' in an edgy all-black outfit that included a sleek cropped bodysuit that highlighted her toned tummy and ample bust

Cool mom: Meanwhile, Mason’s mom, Kourtney Kardashian, looked like the ‘cool mom’ in an edgy all-black outfit that included a sleek cropped bodysuit that highlighted her toned tummy and ample bust

Stylish sisters: Kylie Jenner and Kendall Jenner brought their A-game fashions to Mason's birthday party in town

Stylish sisters: Kylie Jenner and Kendall Jenner brought their A-game fashions to Mason's birthday party in town

Stylish sisters: Kylie Jenner and Kendall Jenner brought their A-game fashions to Mason’s birthday party in town

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

It had long sleeves and an elegant mock neckline.

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

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

Oldest: 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 dressed in a gray jacquard Skims robe with black sunglasses and a black backpack slung over her shoulders.

Mason was also carrying a backpack, along with gray sweatpants and a white t-shirt while wearing a sweatshirt.

The businesswoman was seen with the platinum blonde locks she has rocked all year and the youngster sported a shaggy mushroom cut.

Birthday tribute: Days before the family soiree, Kim penned a sweet birthday tribute to her firstborn nephew Mason.  She took to Instagram Stories to upload a photo of the two standing back to back, proving that Mason had surpassed Kim's 5-foot-2 frame.

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

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

Kourtney Kardashian and Scott Disick’s second child, Reign, shares a birthday with his older brother.

The children were born on December 14, but they are five years apart, and Reign is now eight years old.

His sister, Penelope Scotland Disick, turned ten in July.

Flashback: Kim and Mason pictured together in a flashback photo

Flashback: Kim and Mason pictured together in a flashback photo