After the Queen raised her phone to take a selfie, royalty spotters in Rio noticed a full sized-image of her granddaughter, Princess Estelle, on the back.
“Queen Silvia of Sweden takes the gold medal when it comes to cell phone cases,” wrote American TV station NBC New York.
The Queen, accompanied by King Carl Gustaf, was attending the Equestrian Jumping individual final Round A at the Olympic Equestrian Centre on Friday.
Four-year-old Princess Estelle is the Swedish royal pair's first grandchild. Her baby brother, Prince Oscar, was born in March this year.
The Queen and King also attended Sweden's men's handball matches and were in the crowd in the Maracana Stadium in Rio for last night's women's football final, in which Sweden narrowly missed out on the gold medal to eight-times European champions Germany.