The M-Sport driver clocked the fastest time through the two passes of the famous street stage held around the Unesco World Heritage site in downtown Guanajuato.
Tanak’s times moved the Estonian into a 1.7s advantage over Toyota’s reigning world champion Rovanpera, while Hyundai’s Esapekka Lappi will head into Friday’s gravel stages 2.2s adrift in third.
"Today was a bit of fun, tomorrow is the job," said Tanak, who will open the gravel roads on Friday.
"For sure it will not be an easy day but we need to maximise. Let's see what tomorrow brings - I have never driven in this car on gravel before."
Hyundai’s Thierry Neuville and six-time Rally Mexico winner Sebastien Ogier ended the evening locked together, with the pair tied for fourth, 2.8s adrift of Tanak.
Huge crowds descended upon Guanajuato’s historic streets to welcome the WRC back following its two-year hiatus.
With the road order reversed for the superspecial, it was Tanak, the final Rally1 car to tackle the 1.12km twisty and technical stage, that lit up the timesheets.
The 2019 world champion emerged 0.8s faster than nearest rival Rovanpera, while Lappi posted a benchmark early on that resulted in the third fastest time, 1.3s adrift.
Elfyn Evans was fourth fastest despite flirting with the kerbs located in the cobble stone run through the iconic tunnel section, which this year is adorned with an eye catching mural tribute to the late Ken Block, who died earlier this year.
Neuville was two tenths further back but was faster than his Hyundai team-mate Dani Sordo and Toyota's Ogier, who clocked identical times.
Tanak was 1.8s faster than his first time in the second pass of the stage, which earned him back-to-back stage wins on Thursday night.
Rovanpera once again emerged as his nearest rival although the Finn set an identical time to his countryman Lappi to share the second fastest stage time, 0.9s behind Tanak.
"It is a crazy atmosphere. This kind of stage is not so enjoyable but when you have fans like this it is nice," said Rovanpera.
Ogier was only a tenth back on his second run as he managed to navigate through the tight street stage without issue.
"I feel good," said Ogier. "The real rally starts tomorrow. Tonight was about staying away from the kerb."
Evans will head into Friday’s stages sitting fifth overall, 3.3s from Tanak, after his safe pass through the two stages.
Sordo, M-Sport’s Pierre-Louis Loubet, competing in his first rally outside of Europe, and Toyota’s Takamoto Katsuta completed the top nine positions.
The crews will tackle Mexico’s rough gravel stages on Friday, with the action set to begin on the famous El Chocolate (29,07km) stage at 1448 GMT.
WRC Rally Mexico Classification after Day One
| Cla | Driver/Codriver | Car | Class | Total Time | Gap |
|---|---|---|---|---|---|
| 1 |
 Ott Tanak Martin Jarveoja |
Ford Puma Rally1 | RC1 | 1'54.2 | |
| 2 |
 Kalle Rovanperä Jonne Halttunen |
Toyota GR Yaris Rally1 | RC1 | 1'55.9 | 1.7 |
| 3 |
Esapekka Lappi Janne Ferm |
Hyundai i20 N Rally1 | RC1 | 1'56.4 | 2.2 |
| 4 |
 Sébastien Ogier Vincent Landais |
Toyota GR Yaris Rally1 | RC1 | 1'57.0 | 2.8 |
| 5 |
 Thierry Neuville Martijn Wydaeghe |
Hyundai i20 N Rally1 | RC1 | 1'57.0 | 2.8 |
| 6 |
 Elfyn Evans Scott Martin |
Toyota GR Yaris Rally1 | RC1 | 1'57.5 | 3.3 |
| 7 |
 Dani Sordo Candido Carrera |
Hyundai i20 N Rally1 | RC1 | 1'57.6 | 3.4 |
| 8 |
Pierre-Louis Loubet Nicolas Gilsoul |
Ford Puma Rally1 | RC1 | 1'57.9 | 3.7 |
| 9 |
 Takamoto Katsuta  Aaron Johnston |
Toyota GR Yaris Rally1 | RC1 | 1'58.3 | 4.1 |
| 10 |
Emil Lindholm Reeta Hämäläinen |
Škoda Fabia Rally2 evo | RC2 | 2'00.3 | 6.1 |
| View full results | |||||
