As you probably already know, the One Direction star's mum Johannah Deakin tragically passed away in December last year after a private battle with leukaemia.
Johannah's birthday was on Saturday (March 25) and Louis sent her some birthday love on Twitter, writing "I love you."
Of course, Directioners have been replying with thousands of sweet messages of support and love, which really warms our hearts.
Not long after, Louis took to the stage at the Ultra Music Festival with Steve Aoki to perform 'Just Hold On', which you might remember he bravely sang on The X Factor just days after his mum died.
Louis' younger sis Lottie Tomlinson also honoured her late mum with this touching post on Twitter.
Then on Sunday, the makeup qween followed up with a heartbreaking post for Mother's Day in the UK, which is sadly just one day after Johannah's birthday.
So sad. Sending you and the fam lots of love!