The 23-year-old singer began dating the Victoria's Secret model last year, and the pair are already ''absolutely crazy'' about each other.
A source said: ''They are absolutely crazy about each other, and head over heels in love. They're a great couple, super chill and adorable.''
Despite setting tongues wagging about a speculated engagement after Gigi, 21, was spotted wearing a ring earlier this week, the source claims they loved up couple are ''definitely not'' engaged.
The source told HollywoodLife.com: ''Zayn and Gigi are definitely not engaged, sometimes a tattoo is just a tattoo, and a ring is just a ring! They're both still so young right now, so marriage isn't on the cards just yet -- plus they are both really super focused on their careers right now, they don't have time for distractions.
''I wouldn't be surprised though if an engagement is on the cards in the future however.''
The engagement rumours come after the 'Pillowtalk' hitmaker - who was previously engaged to Little Mix singer Perrie Edwards before their split in 2015 - reportedly popped the question to the blonde beauty before Christmas, only to be turned down.
Gigi reportedly rejected the proposal because she felt it was ''too fast'', and she doesn't want to rush into tying the knot after seeing her mother Yolanda Hadid go through divorce twice.
A source said at the time: ''She's only 21 and doesn't feel ready to tie the knot, so she turned him down.
''She's seen her mom go through two messy divorces, so Gigi wants to make 100 per cent sure Zayn's the one before she makes a lifetime commitment.''
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