The 25-year-old singer remembered her former love, who died in September after an accidental drugs overdose, by writing "Six years" on one of her Instagram Stories, alongside a small white heart.
"The Way", released in 2013, was the first time Ariana and Mac had collaborated together, and also marked the petite singer's first charting song on the Billboard Hot 100 chart.
It included lyrics such as: "If you want it, I got it, I got it everyday, You can get whatever you need from me, Stay by your side, I'll never leave you, And I ain't going nowhere 'cause you're a keeper."
Following the success of "The Way", Ariana collaborated with Mac once again on song "My Favorite Part", taken from the rapper's 2016 album "The Divine Feminine".
Another snap on Monday saw the "7 Rings" hitmaker pose for a selfie with Mac's dog Myron, along with the caption: "Real protective wit my soullll where YOUUUUUU been."
Ariana has maintained a close relationship with the pooch, and has been photographed walking him in recent months, as well as getting a tattoo in the canine's honour. The inking of Myron's name also handily covered up a previous tattoo she'd had done for former fiance Pete Davidson, of his father's firefighter badge number.
Mac adopted the pitbull puppy in early 2017.
Ariana and Mac dated for nearly two years before they split in May 2018. She went on to have a whirlwind relationship with "Saturday Night Live" comedian Pete, which ended in October - just weeks after news broke of Mac's tragic passing.