The 31-year-old stepped down from his role as England captain last April, but has continued to pile on the runs and put on high-quality performances for his nation.
Root also played a major role as England took a 2-0 lead in the three-match Test series against New Zealand.
The ICC said: "Marnus Labuschagne's reign as the highest-ranked Test batter in the world is over as England right-hander Joe Root claimed top spot on the latest ICC MRF Tyres Men's Test Batter rankings.
"Labuschagne rose to the top in December last year following knocks of 103 and 51 against England in Adelaide, but Root's recent run of form has seen the Australian usurped at the head of proceedings.
"Root has already scored four centuries this calendar year and become just the second Englishman to score more than 10,000 Test runs and that has seen the 31-year-old jump in front of Labuschagne as the number one-ranked batter in the world."
Most runs scored by Joe Root in 2022
176 vs New Zealand (Trent Bridge)
153 vs West Indies (Bridgetown)
115* vs New Zealand (Lords)
109 vs West Indies (North Sound)
As things stand, Root has a total of 897 rating point to hie name - five more than second-place Labuschagne.
Fellow Aussie Steve Smith remains third, while Pakistan captain Babar Azam and New Zealand skipper Kane Williamson complete the first five names on the list.
While England can celebrate Root's achievement, they also received some less positive news in the form of a fine from the ICC for slow over-rate in their second Test clash with New Zealand at Trent Bridge.
Cricket's governing body revealed that England have been fined 40% of the match fee and have also lost two World Test Championship points.
The ICC said: "Richie Richardson of the Emirates ICC Elite Panel of Match Referees imposed the sanction after England were ruled to be two overs short of the target after time allowances were taken into consideration.
"In accordance with Article 2.22 of the ICC Code of Conduct for Players and Player Support Personnel, which relates to minimum over-rate offences, players are fined 20 per cent of their match fee for every over their side fails to bowl in the allotted time.
"In addition, as per Article 16.11.2 of the ICC World Test Championship playing conditions, a side is penalised one point for each over short.
"Consequently, two World Test Championship points have been deducted from England's points total."