There was trouble for every car as DRS was disabled due to a technical problem from the start, which led to a more bunched pack for the first 19 laps.
Hamilton led from start to finish, holding off Max Verstappen into the first corner and comfortably pulling away, while his teammate Valtteri Bottas raced into fifth by lap 18 having started on the back of the grid. He would finish fourth with another exceptional performance.
Charles Leclerc struggled with an engine problem throughout, compounding his problems as he was investigated after the finish for fuel irregularities - the Monegasque had started with less fuel than Ferrari had initially submitted.
Hamilton wants new Mercedes contract before summer break
On lap 32 the impressive Verstappen harassed Leclerc into giving up second position, but there was no chance for him to close in on Hamilton who raced faultlessly under no pressure.
The results meant that nothing of note changed at the top of the overall standings, and Hamilton finished this season as he did the last - well ahead of his rivals. With 250 races under his belt he continues to get better.
DRIVER OF THE DAY - Valtteri Bottas
Coming back from last place in the grid to challenge for the podium, even if he didn’t quite make it, shows just how strong Mercedes’ duo is. The focus will obviously be on Hamilton but perhaps next season the gap could close on the Briton, and not just from his colleague.
TALKING POINT - Who can challenge next season?
Bottas, Max Verstappen and Charles Leclerc have all shown this season that they are capable of challenging Hamilton at regular points, but none of them so far have the consistency or exacting quality to launch a title campaign. There is now a chance for them to rest, but more importantly, to refocus and improve for next season. Hamilton could last for years yet.
4/55 - There is a technical problem with DRS, so it is not yet enabled. Leclerc is two seconds behind Hamilton, with Gasly about to be lapped.
9/55 - Leclerc tells his team to check his tires after some 'weird vibrations' - he is having difficulty with his car so far today.
19/55 - DRS has been enabled, meaning there could be more overtaking in the remainder of the race.
27/55 - Verstappen tells his team that 'something is not correct' with his car. Hamilton pits, but has a six-second lead already which seems unsurmountable.
32/55 - Verstappen attacks Leclerc. The Ferrari tries to hold him off but can't, and two turns later Leclerc tries an attack of his own around the outside and couldn't pass him. That's second place for Verstappen and he could hold it now for the rest of the race.
55/55 - HAMILTON WINS! That was never in doubt. Further down the pack, Verstappen is second. Leclerc holds onto third. Bottas recovers into fourth for a great drive. Vettel is fifth, Albon is sixth. Somehow Norris holds Perez off... NO! Perez takes seventh. Kvyat in ninth and Sainz claims 10th for sixth position in the championship.
Spanish Grand Prix
Hamilton overtakes Verstappen to win Spanish GP
Spanish Grand Prix
Lewis Hamilton wins Formula 1 Spanish GP - As it happened