Two points away from defeat, Murray rallied to overcome Radek Stepanek 3-6 3-6 6-0 6-3 7-5 to keep alive his chances of winning a maiden crown at Roland Garros.
By edging the sprightly 37-year-old on another cloudy, windy and cool day in Paris, the Scottish second seed avoided losing in the first round of a major for the first time since the 2008 Australian Open against Jo-Wilfried Tsonga. However the ailing duo of Angelique Kerber, playing her first grand slam match since winning the Australian Open, and Victoria Azarenka departed against Kiki Bertens and Karin Knapp, respectively. Azarenka retired with a knee injury trailing 4-0 in the third set.
Those results make Serena Williams, who spent all of 42 minutes on court, an even stronger favorite in the women's draw.
Stepanek and his all-court game had led two sets to one when darkness halted play Monday, though Murray enjoyed all the momentum with a 4-2 lead in the fourth.
In a tense fifth set that lasted 72 minutes, Stepanek, a showman fueled by fist pumps, clung on desperately in his service games to lead 5-4.
At 30-30 with Murray serving to stay in the match, Stepanek erred on a backhand into the net with space available in the corner. If there was one shot he might rue, that could have been it.
Then at deuce, a 21-shot exchange ensued, which Murray won.
Somewhat deflated at 5-5, Stepanek was broken.
But there was still time for drama. Murray trailed 15-30 serving at 6-5, and later double faulted on a first match point. On the next point at deuce, he almost double faulted long again. Murray finally sealed the affair when Stepanek missed the type of volley he had been making for most of the three hours, 46 minutes the pair played on Philippe Chatrier court. An indication of the battle that transpired, they exchanged a hug at the net.
Murray improved to 21-7 in fifth sets as Stepanek slumped to 15-24 and 1-7 at the French Open.
"It could turn out to be one of the biggest wins of my career," Murray told reporters.
Stepanek swiveled and saluted the crowd as he prepared to leave the stadium, earning a standing ovation, with Murray applauding his beaten foe who has sometimes rubbed his peers the wrong way with his on-court antics.
It was the second near miss for the Czechs in two days, after Lukas Rosol held a 2-1 lead in sets over defending champion Stan Wawrinka prior to the Swiss prevailing Monday.
"Still at 37 years old coming out and fighting like that, playing that way is unbelievable," Murray said. "I don't expect to be doing that myself at that age. I'm just glad I was able to get through.
"He's always been extremely difficult to play but he was serving well. He hardly missed any volleys until the one on match point which almost went over as well. He's using a lot of drop shots, hitting flat. Extremely difficult. I wasn't able to dictate many of the points. Wasn't in a great rhythm. That's a credit to him."
Stepanek nabbed a set off Murray in the quicker environment of Madrid this month but not many had forecast a very tight encounter at the French Open, given the slower conditions and best-of-five set format.
The stoppage Monday certainly helped Stepanek, making for realistically a one-set shootout.
"I knew yesterday I had a bit of momentum when we stopped but I knew that today coming out and just potentially playing a fifth set anything can happen," said Murray. "Both of us had chances in the fifth.
"Thankfully I managed to just get mine in the end when he made a couple of mistakes. I fought extremely hard today and I get a chance to play again tomorrow."
Indeed, Murray takes to the same court Wednesday and he'll be relieved peeking at his immediate draw. French wildcard Mathias Bourgue, ranked 164th and playing in his first grand slam main draw, confronts Murray in the second round.
Murray enjoyed his most consistent clay-court build-up to the French Open this year, and his winning percentage on the sport's slowest surface since 2015 betters world No. 1 Novak Djokovic and record nine-time Roland Garros champion Rafael Nadal.
Nadal, though, had a much easier time Tuesday, playing his fastest ever French Open match. He needed one hour, 22 minutes to dispatch Sam Groth, the Australian with one of the most potent serves in tennis, 6-1 6-1 6-1. The Spaniard even produced a 'tweener -- between the legs -- winner.
Djokovic, seeking to win the only grand slam title to elude him, had to work only fractionally harder, breezing past Taiwan's Yen-Hsun Lu -- who stunned Murray at the 2008 Olympics -- 6-4 6-1 6-1 in 90 minutes.
Injury woes for Kerber
Kerber received a medical timeout for a lingering shoulder issue in her 6-2 3-6 6-3 defeat to 58th-ranked Bertens, winner of a title in Nuremberg last weekend. Kerber pulled out of the event at home due to the shoulder issue.
"I started feeling the pain in the second set," Kerber told reporters. "It was getting worse and worse."
Azarenka took a medical timeout, too. She buckled bouncing to receive serve and later hobbled to the net chasing a shot, before calling it quits in the third against the 118th-ranked Italian, who has underwent heart and knee surgery in her career.
It's a continuation of the former No. 1's health issues. Azarenka was troubled by a back problem this month -- after beginning the season 26-1.
Williams, the intermittent Paris resident and defending champion, crushed Magdalena Rybarikova 6-2 6-0, bypassing the turbulence that filled much of her 2015 tournament. Rybarikova dealt with wrist and knee injuries, not what she needed in attempting to upset the 21-time grand slam champion.
Like Djokovic, Williams addressed the crowd in French in a post-match interview.
Murray was relieved not to say "au revoir."
"Today was tough," he said. "I didn't expect it to be pretty. I just wanted to get through."