He posted a very sweet photo of the pair of them on Instagram, captioned, "Happy birthday to the loveliest person on the planet and one of my best friends @haileesteinfeld . Love ya Hails."
Fans, (and us) instantly started to assume that there could be something going on between the two, with people even commenting things like, "My ship!" on the photo.
However, neither ever confirmed or denied the rumours.
Now, Hailee is talking to Us Weekly about her private life, and the gossip that comes along with being a celeb.
"I feel so lucky that [my fans] care enough about me to know what I’m doing every second of every day, but I think that sometimes it’s hard for people in general to realise that there are boundaries to a person’s life and personal life," she said when she was asked about Niall Horan.
She continued to explain how she is a "very private person" but also said that, "I do love that I have the opportunity to share with them what I’m comfortable with and they’re there to listen and support me."
So, she didn't exactly confirm the rumours, but when she had that chance to outright deny them... she didn't.
Take from that what you will!