The 21-year-old has become the Gunners' second arrival of the summer window following Nuno Tavares's capture from Benfica and leaves Anderlecht after 11 years at the club.
Lokonga is understood to have penned a five-year deal with Arsenal until the summer of 2026, and Anderlecht will reportedly receive up to €21m (£18m) for his sale.
Lokonga's arrival comes at a time where Granit Xhaka is expected to complete a move to Roma, and the Belgium Under-21 international leaves Anderlecht after scoring three goals and assisting seven more in 78 appearances across all competitions.
Here, Sports Mole takes a closer look at Lokonga and what Gunners fans can expect from their side's new lynchpin.
Born in Belgium alongside brother Paul-Jose M'Poku – formerly of Tottenham Hotspur – Lokonga joined Anderlecht's youth academy in 2010 and quickly rose through the youth ranks, penning his first professional deal a couple of weeks after turning 18.
Primarily a number six or box-to-box midfielder who has also had a taste for the right-hand side in his fledgling career, Lokonga scored one goal and assisted one more for the Under-19s in the 2017-18 UEFA Youth League and was handed his senior debut the same season, playing the full 90 minutes on his league debut during a 1-0 win against KAS Eupen.
Lokonga would continue to alternate between the youth and senior teams in the 2018-19 season, during which he also experienced his first taste of Europa League football with Anderlecht, making two appearances off the bench against Spartak Trnava and Fenerbahce.
The 6ft midfielder would go on to establish himself as a regular for Anderlecht's first team in the 2019-20 season, claiming three assists from 23 Jupiler Pro League appearances, and he has earned plaudits for being adept in the tackle, his wide range of passing and exceptional close control to emerge victorious from tight midfield battles.
After establishing himself as a mainstay in the Anderlecht team during the disrupted 2019-20 campaign, Lokonga would proceed to enjoy his strongest and most eye-catching run in the side last term under Vincent Kompany.
The 21-year-old scored his first goal at senior level in a 1-1 draw with KAS Eupen – the side he made his Belgian top-flight debut against – back in September 2020, although he went from hero to zero in their next game versus Club Brugge as he was dismissed for two bookable offences.
However, 90 minutes of football week in week out would follow for Lokonga after his suspension, and his second goal of the season would come in a 2-2 draw with Zulte Waregem, one week before Kompany would hand him the captain's armband for the remainder of the season.
Lokonga battled adductor problems for a small portion of January, but he played every minute of Anderlecht's last 11 league matches donning the skipper's armband at the ripe old age of 21, and he avenged his previous sending off against rivals Brugge by netting the winner against them in a 2-1 success during the penultimate weekend of the campaign.
Lokonga first pulled on the Belgium shirt for an Under-17s friendly against the Czech Republic, and he would go on to make a solitary appearance for the Under-19s versus France before making a name for himself at the next level up.
The Arsenal man would become a regular for the Under-21s during their bid to qualify for the recently-concluded European Championship, and he netted two of his side's five goals in a 5-0 drubbing of Wales in qualification Group 9.
Belgium's starlets would ultimately fail to qualify for the final tournament, but Lokonga had already done enough to earn his first call-up to the senior side, and he was an unused substitute in June's friendly draw with Greece just before the Euros.
Anderlecht boss Kompany tipped Lokonga to force his way into Roberto Martinez's final 26-man squad for Euro 2020, but he ultimately had to settle for a place on the reserve list, although he still had the pleasure of sharing the same training pitch with arguably Arsenal's greatest ever player Thierry Henry.
Henry reportedly put in a good word for Lokonga and urged the Gunners to strike a deal for the up-and-coming midfielder - advice that Mikel Arteta and Edu took - and Gooners are relishing the chance to watch the energetic starlet in pre-season action at the Florida Cup.
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