Gennady Golovkin’s streak of 23 straight knockouts came to an end against Brooklyn’s Daniel Jacobs, who forced “GGG” to go 12 rounds for the first time in his career Saturday night at Madison Square Garden in front of a crowd of 19,939. But the fighter from Kazakhstan somehow managed to remain undefeated by unanimous decision and add Jacobs’ WBA middleweight title belt to a collection that already included the WBC, IBF and IBO titles.

Golovkin (37-0, 33 KOs) knocked down Jacobs (32-2, 29 KOs) in the fourth round, but Jacobs recovered well and used his size and speed to keep Golovkin at bay much of the night and turn him into more of a boxer than the power puncher he normally is.

Gracious in victory, Golovkin said, “Daniel had a very good jab, a very clean jab. Daniel is my favorite fighter. I can’t destroy him. He’s a very good fighter . . . I respect this man.”

Judges Don Trella and Steve Weisfeld scored it 115-112, and Max DeLuca scored it 114-113. Jacobs, who won the 12th on two cards, was a 115-113 winner on the Newsday card.

According to CompuBox, Golovkin landed 105 jabs compared to only 31 by Jacobs, but Jacobs scored more power punches, 144-126.

“I think I won the fight,” Jacobs said. “I won it by at least two rounds minimum.”

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Golovkin went from 159.6 at the official weigh-in to 169.6 for the IBF fight-day weigh-in. Jacobs weighed 159.8 on Friday but obviously was over 170 pounds by Saturday morning, and skipped the IBF weigh-in, forfeiting a shot at that title.

The first round was a tentative feeling-out process in which little of consequence happened. Jacobs surprised in the second by switching to a southpaw stance and landing a left hook out of it. He reverted to orthodox style and continued to jab well. In the third, Jacobs landed a sharp counter left, fought well out of the clinch and ended the round with a hard right.

The tenor of the fight changed early in the fourth round when Golovkin finally moved in a landed a crushing right to Jacobs’ jaw and followed it up with another sharp right that sent Jacobs down for the third time in his career. Jacobs got up and was eager to get going and fought back at the end of the round.

“After the knockdown, I told him he had to kill me,” Jacobs said. “There were many times during the fight I went toe-to-toe because I knew I could.”

But the fifth started with another hard shot from Golovkin, this time a left hand that rocked Jacobs and roused the crowd.

By the sixth, Jacobs had regrouped, He clipped Golovkin with an overhand right early and put together some effective combination punching to the body. At the end, he landed a left-uppercut followed by a right hand for his strongest round to that point. Golovkin landed the hardest punch of the seventh, a lead right that drove Jacobs backward, but the Brooklyn fighter shook it off and continued to outpunch Golovkin in terms of volume. At the end of the round as the ball rang, he shoved GGG as if to say, “I’m not going away.”

Although Golovkin stalked as he normally does and tried to cut off the ring, Jacobs’ hand speed posed a problem getting close. In the eighth, he moved in effectively behind his jab and delivered flurries to Golovkin before moving away. But in the ninth, Golovkin turned the tables with a right uppercut that stunned Jacobs with little over a minute left in the round. GGG landed two more uppercuts along with a bevy of right-hand power shots. During the 10th, Golovkin stayed close, pressing Jacobs toward the ropes. At the end, Jacobs landed a sharp left hook, but it didn’t faze Golovkin.

The tide swept back and forth, and even with the Garden crowd urging Golovkin with chants of “Triple-G,” it was Jacobs who rose to the occasion near the end of the 11th round to land a big left hook followed by a left-right combo before the bell that has him exulting.

Obviously inspired, Jacobs came on strong in the final round, outpunching Golovkin before the final bell.