"I needed this pole - I've not had one for a while", said Hamilton who leads Vettel in the drivers' title race by just four points after four races.
Having looked solid throughout the weekend, Saturday's pole sitter recorded his 64th career win, ensuring Ferrari stood no chance against an invincible Mercedes team that delivered an error-free weekend.
He joined seven-time champion Schumacher and two-time champion Mika Hakkinen as a three-time victor in Spain.
"I'm OK", he responded on the team's radio link.
His teammate Valtteri Bottas completed over 20 seconds behind with Crimson Bull's Max Verstappen finishing the rostrum.
With Hamilton once again in clean air out front he held the lead on Vettel at over ten-seconds, when the virtual safety vehicle was deployed after Esteban Ocon's retired at the side of the track on lap 41. "I think it was the right thing to do".
Spanish duo Carlos Sainz and Fernando Alonso claimed seventh and eighth, while Sergio Perez earned Force India two points.
On a cooler day with intermittent sunshine and heavy clouds looming, the track temperature was 35 degrees Celsius, and the air 15, when the race began.
The red lights' exodus saw the red auto of Sebastian Vettel push past Mercedes' Valtteri Bottas into the first corner, staggering the Mercedes-Ferrari running order. The Frenchman then speared across the circuit, into Renault's Nico Hülkenberg and Toro Rosso-Honda's Pierre Gasly, both of whom suffered race-ending damage in the collision.
All were unhurt, although Grosjean had to go to the medical centre for a precautionary check because the incident triggered the high impact alert in the vehicle.
The British driver was able to stretch out a comfortable lead out and when Ferrari opted to stop Vettel on lap 18 for the medium tyre, Hamilton was seven seconds clear.
Hamilton has been desperate for a return to form over the single lap and with his Mercedes finally performing as expected and required he managed it superbly.
But, after three pole positions in a row in Bahrain, China and Azerbaijan, the German will have to try to win from behind in Spain.
He now has 95 points to Vettel's 78 after five rounds of the 21-race championship.
After 40 of the 66 laps, Esteban Ocon pulled up after an engine failure, bringing Virtual Safety Car (VSC) conditions.
Vettel dropped to fourth from second when Ferrari made a decision to pit him under the virtual safety auto so he could attack the last part of the race with fresher tyres.
By this point, Vettel had gotten ahead of Bottas for scond place and was hoping to chase after Lewis Hamilton who had maintained his lead from pole position.