Robert Pattinson and Kristen Stewart engaged? Twilight stars shop for rings in West Hollywood
Kristen, 22, was looking at quirky pieces with different coloured diamonds, according to onlookers at the city's Neil Lane shop.
'She loves Rob, and she's finally ready - and engagement is a logical next step,' a friend tells Metro.
'In the past year, they've really heated up - moving in together, travelling together, introducing each other to friends.'
The couple, who met while playing the roles of Bella Swan and Edward Cullen in the Twilight films, are notoriously cagey about their romance and rarely talk about each other.
But they've become more open in the past few months and were pictured kissing for the first time at Cannes Film Festival in May.
However, if Kristen has become engaged to Robert, 26, it's very unlikely that she'll announce it.
'I guarantee whenever I get married or have a baby, everyone is going to want to know my kid's name and I'm not going to say it for ages,' Kristen told GQ last year.
'That's just the way I want to do it. It'll come out but it won't have come from me.
'They're going to be really p*ssed off.'