Saturday in Spain maybe saw the start of the Hamilton fightback as he took a superb pole -- his first in three races -- relegating Rosberg to second on the grid.
Hamilton dominated the second and then decisive third qualifying sessions at the Circuit de Catalunya to record a fastest time of one minute 22 seconds, 0.280 seconds quicker than his title rival.
The Briton has been on pole in two previous occasions this season, but poor starts undermined his challenge, a situation that Hamilton is determined to improve upon.
"We've been working on our starts. I'm in the best place to start from and tomorrow's a huge day," he told the post-qualifying media conference.
Rosberg, who has won the first four races of the campaign and seven in a row to open up a 43-point gap over Hamilton, is still confident he can make it eight straight.
"For sure, I'm disappointed -- I wanted to be first. Fortunately it's the race that counts," said the German.
Behind the dominant Mercedes pair there was a superb performance from the Red Bull duo of Daniel Ricciardo and in particular Dutch teenager Max Verstappen, who has replaced Daniil Kvyat in the team.
Ricciardo responded to the fast times set by his youthful teammate to edge him for third spot in Q3, but the switch of Verstappen, who started the season with the sister Toro Rosso team, with Russia's Kvyat clearly paid off .
"Amazing from our drivers. Daniel's last lap was mighty and Max's first #Quali was incredible," team chief Christian Horner tweeted.
It left the Ferraris of Kimi Raikkonen and four-time champion Sebastian Vettel on the third row in fifth and sixth places.
Finn Valtteri Bottas was seventh for Williams ahead of Spaniard Carlos Sainz in the Toro Rosso with Sergio Perez of Force India in ninth.
There was a boost for home fans as two-time champion Fernando Alonso finally made the final session of qualifying in his McLaren Honda, taking 10th on the grid.
Hamilton's pole was the 52nd of his career, the third best record of all-time, with only Michael Schumacher and Ayrton Senna ahead of him.