His 21st-minute strike from outside of the area, one of two goals in United's 3-1 victory, means the 35-year-old has scored the 25,000th goal in the Premier League era.
"I thought that was only me who had scored 25,000," Ibrahimovic joked after the match.
The goal was a memorable way for Ibrahimovic to get back on the scoresheet as he had gone six PL matches without finding the net. His last goal came in the defeat by Manchester City in September.
It is the first time that Man Utd have scored a landmark goal in the Premier League, although they were the side who conceded the first PL goal, when Brian Deane headed home against them for Sheffield United in 1992.
With 17 goals scored on Saturday, Sunday's action started with 24,992 goals scored in the competition.
Paul Pogba scored the 24,999th goal six minutes earlier when he put United ahead at the Liberty Stadium while Roberto Firmino netted the 25,001st goal, 11 minutes after Ibrahimovic, scoring Liverpool's fourth goal against Watford.
|1st||15 Aug 1992||Brian Deane||Sheff Utd v Man Utd|
|100th||25 Aug 1992||Eric Cantona||Leeds Utd v Spurs|
|1,000th||7 Apr 1993||Mike Newell||Nott'm Forest v Blackburn|
|5,000th||7 Dec 1996||Andy Townsend||Southampton v Aston Villa|
|10,000th||15 Dec 2001||Les Ferdinand||Spurs v Fulham|
|15,000th||30 Dec 2006||Moritz Volz||Chelsea v Fulham|
|20,000th||21 Dec 2011||Marc Albrighton||Aston Villa v Arsenal|
|25,000th||06 Nov 2016||Zlatan Ibrahimovic||Swansea v Man Utd|