The teams clash in Cape Town with the series all square at 1-1 after the Springboks claimed a narrow 32-29 win in the first test in Pretoria, but were beaten 13-12 last weekend in Bloemfontein as Wales claimed a first away test win against South Africa.
Biggar has overcome a worrying shoulder problem to take his place at fly half as coach Wayne Pivac has made just one enforced change from the second test after an injury to winger Alex Cuthbert (32).
"It's a great opportunity for us to win a series here, which if I said this four or five weeks ago, before we flew out, I'd probably have been laughed out of town," Biggar told reporters on Thursday.
"So it's definitely not one to miss. We're really looking forward to it as a group, we've put a huge amount into this tour in terms of the training we've done, the amount of sacrifices we've made, and we've worked our absolute socks off. So it'd be brilliant to get full reward at the end of Saturday.
"We know this is our last week of the season, so we can go out and give absolutely everything, leave it all out there."
The 'Boks have reverted to something like their first-choice selection after making 14 changes for the second test, as they try to protect a proud record of having not lost a home test series of two or more games since the British & Irish Lions claimed a 2-1 success in 1997.
The Boks were poor with their execution in the first two games of this series and were kept tryless in the second test for the first time in 43 matches.
"We have to get dominance in the set pieces, so we have to be solid in the scrums, lineouts and mauls, and hopefully this will create space for guys like Cheslin (Kolbe) and the backs to get opportunities out wide," Bok prop Steven Kitshoff (30) said.
"We have put in the same preparation this week and we now have to ensure that we perform. We understand as a team how important it is to beat Wales."
