She's never stopped believing and now Tatjana Maria is three matches from becoming the first tennis mum since the great Evonne Goolagong Cawley in 1980 to win Wimbledon.

Maria saved two match points on Sunday to continue her giant-killing run through the draw and reach her maiden grand slam quarter-final at age 34.

Tunisian third seed Ons Jabeur, the highest-ranked still standing, also rolled on with a hard-earned 7-6 (11-9) 6-4 victory over Elise Mertens.

But it's Maria who is suddenly the talk of the tournament.

The world No.103 upset 12th seed Jelena Ostapenko 5-7 7-5 7-5 to add the 2017 French Open champion to her growing list of scalps this remarkable campaign.

The mother of two and the oldest woman left in the draw had already eliminated Greek fifth seed Maria Sakkari and Australian qualifier Astra Sharma to make the second week at a major for the first time in 35 attempts.

Maria saved the two match points at 4-5 in the second set before running down Ostapenko and sealing victory in two hours and eight minutes.

With a previous best grand slam result coming with a third-round appearance at Wimbledon in 2015, the German will play compatriot Julie Niemeier on Tuesday for a most improbable place in the last four.

"There's always the belief that I can do it," said Maria, who had her first daughter in 2013, then a second last April.

"That's why I came back after the first one. It's why I came back after the second one. If not, if I don't believe I can do these things, then I would not be here.

"So there's always this believing and keep going and improving and trying my best at the end.

"I'm now in the quarter-final of Wimbledon, so it's really amazing for me.

"This means also that you always have to keep going. Doesn't matter how old you are, doesn't matter how many kids you have - you just have to keep going and to believe in yourself."

If Maria goes on and lifts the Venus Rosewater Dish on Saturday, she'll have achieved a feat that not even Serena Williams has managed.

Still chasing a record-equalling 24th grand slam crown, Serena lost the 2018 and 2019 Wimbledon finals after having daughter Alexis Olympia in 2017.

After ousting second seed Anett Kontaveit in the second round, Wimbledon newcomer Niemeier crashed Heather Watson's party with a 6-2 6-4 last-16 win over Britain's last women's singles hope.

"I can't believe it. I want to say sorry I had to kick out a British player today. The atmosphere was incredible," said Niemeier, playing only her second grand slam tournament.

New title favourite Jabeur will play Marie Bouzkova next after the Czech was the first player through to the quarter-finals after beating Frenchwoman Caroline Garcia 7-5 6-2.

Elena Rybakina, the 17th seed, was the first player on Monday to make the quarter-finals from the top half of the draw.

The Kazakh beat Croatia's Petra Martic 7-5 6-3 and will next play Australian Ajla Tomljanovic or Alize Cornet, the Frenchwoman who shattered world No.1 Iga Swiatek's 37-match winning streak in the third round.