Giroud's previous deal was due to run out at the end of next season, but it has now been confirmed he will remain at the Emirates Stadium alongside Laurent Koscielny and Francis Coquelin, per the Gunners' official Twitter account:
After Giroud signed the deal on Thursday, Arsenal manager Arsene Wenger told the club's official website: "We are very pleased that three important members of our team have committed to us for the long term. ... Olivier has big experience in the game now and has become a more and more complete player since joining us."
The decision to keep Giroud at the club could be deemed a slightly surprising one, particularly considering the striker has seen his game time limited to just three starting appearances in the Premier League this season.
He has, however, remained a threat when handed an opportunity, bagging nine goals and five assists in all competitions. The France international's latest strike came as Arsenal beat Preston North End 2-1 in the FA Cup third round.
OptaJoe highlighted Giroud's fine recent run of form:
Much of Giroud's time on the sidelines has been due to the stunning performances of Alexis Sanchez in the central-striker role for Arsenal. The Chile international has netted 15 goals and proved he relishes being the main man up front.
Giroud, 30, has often attracted criticism for a lack of pace and his goal record. However, last season he struck the back of the net 28 times for club and country, with 16 of those goals coming for Arsenal in the league.
The forward pointed to his goal record for the Gunners last season when defending himself against criticism at Euro 2016 in the summer.
Per L'Equipe (h/t Mark Rodden of ESPN FC), Giroud said:
I recall that the season did not start in January 2016, even if it suits guys who are coming down on me at the moment to count on certain periods rather than others.
A striker should be judged on continuity. I had six very good months and three months after that which were a bit more difficult.
But in the end, I scored 28 goals [for club and country] and had six assists. It's one of the best seasons of my career.
While Arsenal tend to look a more dangerous and fluid attacking proposition when Sanchez leads the line, Giroud's aerial expertise continues to offer a useful alternative for Wenger.
The news of Giroud's commitment comes as Arsenal look to tie down Sanchez and Mesut Ozil to new deals, as club secretary David Miles confirmed to BT Sport. Both players have 18 months left on their contracts, and the club hierarchy will be keen to secure their two leading stars rather than see them lured away by rival clubs.