Arsenal had taken the lead in the first half when Bukayo Saka struck, but a Gabriel own-goal made it 1-1 at the break.
The Gunners fought hard to claim the win in the second-half and they are now just two points off League leaders Liverpool.
Simon Collings was at Emirates Stadium to see Arsenal in action...
Distribution was excellent and he set Martinelli away for a good chance early on. Arguably should have been more dominant for Liverpool's equaliser.
Looks fitter than he has in recent weeks. Beat Curtis Jones twice with some great footwork and got forward when he could.
Failed to deal with a ball over the top, which allowed Liverpool to equalise just before the break. A rare error from the Frenchman during a rare poor performance.
Unfortunate to score an own-goal as Diaz's cut-back went in off his hand. Helped make amends with a ball over the top that Martinelli scored from.
Taken off at half-time, for what must have been an injury. The Ukrainian had been solid in the first-half, especially in possession.
Played a great pass to help create the opening goal. Was relentless with his pressing up top. A captain's peformance.
Was everywhere and bossed the midfield. Continues to deliver in the biggest games for Arsenal. Worth every penny of the £105million Arsenal paid.
Brought into the midfield as a way of giving Arsenal more control and was excellent. Rolled back the years with one of his best performances for the Gunners.
Bukayo Saka 7
Opened the scoring by finishing off Havertz's saved effort. Looks reenergised after the winter break and now has two goals in as many games.
Kai Havertz 7
Given the nod as the No9 in the absence of Gabriel Jesus. Missed a great chance when set through, but Saka scored the rebound. Hold-up play was vital for Arsenal.
Gabriel Martinelli 9 | Star player
An electric performance. Caused Liverpool's defence so many problems with his pace. Fully deserving of his goal, which came from more hard work off the ball.
Jakub Kiwior (Zinchenko 45') 6
On at half-time and did well in a game of this magnitude. Missed a great chance late on.
Leandro Trossard (Martinelli 74') 7
Off the bench and scored Arsenal's third goal with a brilliant run and finish.
Reiss Nelson (Saka 79') N/A
Subs not used: Ramsdale, Cedric, Walters, Elneny, Smith Rowe, Nketiah