Rumours started circulating around the couple back in March when the two were spotted out on a stroll in New York City, but up until now, they've kept their relationship under the radar, an impressive feat for any celebrity in the age of social media.
Arnett is a vocalist in the band Milo Greene, and if his Instagram is any indication, his sense of humour — he recently posted a photo of Passport to Paris, the tween comedy starring Olsen's older sisters Mary-Kate and Ashley, with the caption "it's going 2 b in seine" — is just as solid as his musical skills.
The pair looked radiant as they were photographed for the first time together as an official couple. Olsen kept things neutral in a gorgeous cream dress and berry lipstick, while Arnett donned a sheer blush button-down shirt and disheveled locks. I don't want to say that they coordinated outfits, but those dreamy, soft colours work just so well together.
It's great to see Olsen so happy after her split with ex-fiancé, Narcos star Boyd Holbrook, whom she was with for three years. Maybe her budding relationship will give her a reason to post more frequently on her new Instagram account? That is, if she can make space for him with all of the sponsored content she hopes to post! (Hey, girl, do what you have to do and get that money.)
But Arnett isn't the only one keeping Olsen busy and smiling these days. Last week, Netflix announced it would acquire her latest film, Kodachrome, for a whopping $4 million (£2.9 million), and she'll return to the big screen next year as the Scarlet Witch in Avengers: Infinity War.