Mkhitaryan, who moved to the Emirates Stadium in January 2018 from Manchester United, made 59 appearances in all competitions for the Gunners, scoring nine goals.
A club statement read: "Everyone at Arsenal wishes Micki all the best for his season with Roma. The loan is subject to the completion of regulatory processes."
Darmian, meanwhile, is the fourth player to leave Ole Gunnar Solskjaer's side for Serie A this summer, with Romelu Lukaku and Alexis Sanchez having joined Inter Milan before Chris Smalling made his loan switch to Roma last week.
Darmian has long yearned for a return to Italy and the PA news agency understands Parma are paying around four million euros (£3.6m) for the versatile full-back.
The deal is also believed to include a sell-on clause, with the Italy international signing a deal until 2023 at the Stadio Ennio Tardini.
Darmian joined United in 2015 from Torino in a reported £12.7m deal and went on to represent the club 92 times in all competitions.
Solskjaer confirmed on Friday that a move was on the cards for the full-back and the following day reiterated that Paul Pogba would not be leaving for Real Madrid or anywhere else before the European deadline.
"Paul Pogba will be playing for us," the United boss said after Saturday's 1-1 draw at Southampton.
As part of the deal, Icardi signed a two-year contract extension with Inter, but the agreement also includes a permanent move clause for €65m [£59m].
"I will give everything to help my new team go as far as possible in all competitions," Icardi said. "Paris Saintt-Germain has become an international football powerhouse, attracting some of the greatest players in recent years.
"The momentum is strong in Paris, ambitions are high and I am sure that we have everything here to go even further."
PSG also secured the signing of goalkeeper Keylor Navas on a four-year deal from Real Madrid.
Liverpool have sold youth-team striker Bobby Duncan to Fiorentina after the Serie A side made an offer to buy him permanently.
It is understood the Italians have paid €2m (£1.7m) up front with a 20 per cent sell-on fee for the player.
Last week the club were firm in their stance that the 18-year-old, a scorer of 32 goals for the under-18s in his first season since arriving from Manchester City, would not be leaving.
Javier Hernandez has left West Ham for Spanish side Sevilla, with Hammers co-owner David Gold confirming the news on social media.
The official club social channel announced that the Mexican forward had moved to Sevilla on a permanent basis for an undisclosed fee.
Bournemouth goalkeeper Asmir Begovic has moved to Azerbaijan outfit Qarabag on loan, while Brighton frontman Florin Andone has joined Turkish champions Galatasaray on a season-long loan.
Brighton have retained an option to recall Andone in January as part of the agreement.
The 26-year-old came off the bench to score in the opening-day win at Watford but was sent off on his first start of the season in the home defeat to Southampton.
Begovic has made 62 appearances for Bournemouth in the Premier League since signing from Chelsea in a £10m deal the summer of 2017.
But he has fallen out of favour and has not featured for Eddie Howe's side this season with Aaron Ramsdale, Mark Travers and Artur Boruc ahead of him in the pecking order.
Former Tottenham striker Fernando Llorente has joined Serie A side Napoli.
The Spanish forward already has two Scudetto titles from his time in Italy with Juventus between 2013 and 2015.
At the north London side, he scored 13 goals in 66 appearances, including significant goals last season against Borussia Dortmund and Manchester City as Tottenham reached the final of the Champions League.
Llorente had been without a club since he left Spurs at the end of his contract in June.
Chelsea winger Kenedy has completed a season-long loan move to Spanish club Getafe.
The Brazilian, who is in the final year of his contract, spent the last 18 months on loan at Newcastle, where he scored three goals in 41 appearances.
Despite featuring in Chelsea's pre-season preparations, Kenedy has failed to break into Frank Lampard's first-team squad for the Premier League campaign.
Since joining the Blues from Fluminense in 2015, Kenedy has made 27 appearances and was an unused substitute in the first two league games of this season.
Southampton midfielder Mario Lemina has joined Galatasaray on a season-long loan.
Lemina, who turned 26 on Sunday, has made 52 appearances since arriving at St Mary's from Juventus in 2017.
The Gabon international follows former Premier League players Ryan Babel, Steven Nzonzi and Sofiane Feghouli to the Turk Telekom Stadium.
Celtic have signed teenage defender Jeremie Frimpong from Manchester City.
The 18-year-old right-back has agreed a four-year contract with the Scottish champions.
Striker Stefano Okaka has joined Udinese from Watford on a permanent deal.
The 30-year-old has signed a three-year contract, keeping him at the Italian club until 2022.
Okaka spent the second half of last season on loan at Udinese and scored six goals in 16 appearances for the Serie A club.
The Italy international moved to Watford from Anderlecht in 2016 and scored five goals in 39 appearances for the Hornets.
He last played in Italy for Sampdoria, having previously had spells at Parma, Bari, Brescia, Modena and Roma.
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