Jon Hamm's Fiancée Anna Osceola Debuts Her Engagement Ring — and So Does Mad Men Costar Christina Hendricks

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We caught a glimpse of not one, but two stunning new celebrity engagement rings at the Oscars 2023 afterparties — with both Jon Hamm's fiancée Anna Osceola and his Mad Men costar Christina Hendricks debuting their new bling.

Hamm, 51, and Osceola, 34, were at the Vanity Fair Oscar afterparty alongside a star-studded guestlist that included best actress Michele Yeoh and best actor Brendan Fraser.

Osceola's engagement ring appears to be a simple (but unmissable) emerald-cut solitaire diamond — the standout in an otherwise understated jewelry look to go wit the black-and-white gown sparkling green clutch she wore to the Vanity Fair party. Her fiancé complemented her ensemble in a classic tux.

Hamm and Osceola first reportedly met on the set of the AMC series Mad Men in 2015, before being spotted together on several occasions and were romantically linked in 2020. PEOPLE confirmed their engagement news in February 2023.

Matt Winkelmeyer/VF23/WireImage for Vanity Fair

RELATED: Christina Hendricks Engaged to George Bianchini After They 'Proposed to Each Other'

Meanwhile, Hendricks, 47, was at the Elton John AIDS Foundation's 31st Annual Academy Awards Viewing Party with husband-to-be, camera operator George Bianchini.

Similar to her fellow Mad Men costars, Hendricks had only recently confirmed her engagement to Bianchini.

Taking to Instagram to announce the happy news on March 10, Hendricks said "We proposed to each other and we said yes!!! I will love and care for him forever."

In a statement to PEOPLE, Hendricks said "We started dating in 2020. The proposals were quiet and romantic and done separately in special places that have meaning to us."

Earl Gibson III/Shutterstock; Vivien Killilea/Getty Images for Tequila Don Julio

RELATED: Jon Hamm Says He's 'Very Much' in Love with Anna Osceola

Hendricks' engagement ring appears to be a vintage-inspired style, with multiple diamonds inset into an intricate design on the band. The actress wore a turquoise gown to the Oscars viewing party and Bianchini sported a tuxedo speckled with Swiss dot embossing.

Emma Watson, Heidi Klum and Hilary Duff were among the many stars who also attended the Elton John event.

Hamm and Hendricks starred together in the critically-acclaimed Mad Men, and Osceola appeared in the series' final episode. She had a small role, playing the receptionist at Esalen, a spiritual California retreat that Hamm's character (Don Draper) attended.

At the time, Hamm, was in a long-term relationship with Jennifer Westfeldt. The couple split months later after 18 years together.

Hamm and Osceola joined forces onscreen again in 2022, for the third installment of the Fletch series, Fletch, Confess. In it, Hamm takes on the role of semi-retired journalist Irwin M. Fletcher (originally played by Chevy Chase in 1985 and 1989), while Osceola appears in the project, playing the role of "Larry."

RELATED: Who Is Jon Hamm's Fiancée? All About Anna Osceola

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Hendricks and Bianchini worked together on the first season of her NBC crime comedy-drama Good Girls, which premiered in 2018 and ended after 4 seasons in 2021. They were first romantically linked in November 2021 when they attended a Christian Siriano exhibit together in Georgia

Christina Hendricks/instagram

Hendricks was previously married to actor Geoffrey Arend; they filed for divorce in 2019.