Humbert trailed 2-5 in the second set and faced the match points at 3-5, then turned things around to clinch a 6-7 (4), 7-6 (5), 7-6 (5) win after nearly three hours.
Wawrinka won the last of his three Grand Slam titles at the 2016 US Open but was then hit by multiple injuries and is now ranked 20th in the world.
Rotterdam Open 2020: Unseeded Slovenian Aljaz Bedene upsets World No 6 Stefanos Tsitsipas in straight sets to book quarter-final spot
Russian Andrey Rublev continued his impressive form with a 7-5, 6-3 victory over Alexander Bublik to extend his win record in 2020 to 13-1
US Open 2019: Alexander Zverev beats Aljaz Bedene to reach fourth round for first time at Flushing Meadows
Alexander Zverev progressed to the last 16 at the US Open for the first time with a hard-fought win over Slovenia's Aljaz Bedene.
Rio Open: Dominic Thiem bows out in first round after shock defeat to Laslo Derje; Aljaz Bedene beats Marco Cecchinato
Top seed Dominic Thiem was knocked out the Rio Open in the first round on Tuesday, going down 6-3, 6-3 to Laslo Derje, a result that gave the unheralded Serbian his first victory over a top 10 player in his career.
Australian Open 2019: South Korea's Hyeon Chung solves five-set puzzle against Bradley Klahn to win first match of the year
In the final analysis, Klahn had 84 unforced errors and 58 winners, while Chung was a lot sounder at 34 winners and 35 unforced errors. Slow and steady, the Korean finally won in three hours and 37 minutes.
Australian Open 2019: Fourth seed Alexander Zverev cruises into second round with comfortable win over Aljaz Bedene
Alexander Zverev has been tipped as a potential Grand Slam winner and lived up to his billing by sweeping into the second round of the Australian Open.
Brisbane International: Milos Raonic, Grigor Dimitrov storm into 2nd round; Karolina Pliskova fight back to win opening tie
Former champions Milos Raonic and Grigor Dimitrov stormed into the second round of the season-opening Brisbane International tennis tournament with comprehensive wins on Monday.
Stan Wawrinka motors along after comeback, but worrying signs about his long-term future hard to ignore
The Wawrinka we have come to admire (and fear) has never been a small-tournament or small-opponent guy. But is that just our spoiled selves talking? Would it really be such a bad thing if Wawrinka never reached another Slam final?
Three-time Grand Slam champion Stan Wawrinka booked a place in the second round at the Saint Petersburg Open with a hard-fought straight-sets win over Slovenia's Aljaz Bedene at Saint Petersburg on Monday.
Wimbledon 2018: John Isner survives massive scare against Ruben Bemelman to win 5-setter in second round
Isner led two sets to love and held a match point in the third set but the 105th-ranked Bemelmans stormed back to win two tiebreaks and level the match before rain intervened
Six days after being knocked out in the qualifying round, Italian 25-year-old Marco Cecchinato made the most of a reprieve to reach the Hungarian Open final on Saturday.
Monte Carlo Masters: Rafael Nadal says he won't skip tournaments to lengthen career like rival Roger Federer
Federer is missing the claycourt season for the second year in a row, but Nadal says he has no plans to skip any Grand Slam tournaments in the near future.
Monte Carlo Masters: Novak Djokovic battles past Borna Coric; Rafael Nadal cruises through to second round
Djokovic, playing only his fourth tournament since Wimbledon last July after struggling with a right elbow injury, overcame some late nerves to win 7-6 (2), 7-5.
Argentina Open: Dominic Thiem coasts past Aljaz Bedene to win second Buenos Aires title in three years
Dominic Thiem defeated Aljaz Bedene 6-2, 6-4 in one hour and 31 minutes to extend his perfect record at the tournament, having captured the trophy also in 2016.
Federer said some of his fellow players struggle with their media obligations, fearful of being misinterpreted.
Australian Open 2018: Roger Federer begins title defence in style, heavily-strapped Garbine Muguruza advances
Federer, rated as the favourite to win his 20th Grand Slam title, thrilled the Rod Laver Arena crowd with a virtuoso performance.
Australian Open 2018: Roger Federer faces Aljaz Bedene in opener, Rafael Nadal to take on Victor Estrella Burgos
Roger Federer will open his title defence against Slovenia's Aljaz Bedene and has a potential quarter-final with David Goffin in the Australian Open
Wimbledon stars came under fire on Tuesday for their treatment of ballboys after Rafael Nadal was derided for handing rubbish to one youngster to deposit in a bin right beside him
Wimbledon 2017, Day 5 highlights: From 'Alona' Ostapenko to Mischa Zverev's plan to unsettle Roger Federer
A look at some of the off-court highlights from Day 5 of Wimbledon 2017.