His Anfield future became the subject of intense speculation after a dramatic bust-up with Liverpool manager Arne Slot in December.
He accused Liverpool of throwing him "under the bus" after he was benched for three games in a row and said he had no relationship with the Dutch boss.
'The day has come'
Salah, in a video on social media featuring highlights of his time with Liverpool, said: "Hello everyone. Unfortunately, the day has come.
"This is the first part of my farewell. I will be leaving Liverpool at the end of the season.
"I wanted to start by saying that I never imagined how deeply this club, this city, these people would become part of my life. Liverpool is not just a football club.
"It's a passion, it's a history, it's a spirit. I can't explain in words to anyone not of this club."
Salah, who in common with many Liverpool players and staff was deeply affected by the death of team-mate Diogo Jota in a car crash in July, added: "We celebrated victory, we won the most important trophies and we fought together through the hardest time in our life.
"I want to thank everyone who was part of this club throughout my time here, especially the teammates past and present.
"And to the fans, I don't have enough words. The support you showed me through the best time of my career, and you stood by me in the toughest times. It's something I will never forget and something I will take with me always.
"Leaving is never easy. You gave me the best time of my life. I will be always one of you. This club will always be my home, to me and to my family.
"Thank you for everything. Because of all of you, I will never walk alone," insisted Salah in a reference to the Liverpool fans' anthem.
'Perfect send-off'
Salah's agent, Ramy Abbas Issa, posted on X: "We do not know where Mohamed will play next season. This also means that no one else knows."
Liverpool said on their website: "Mohamed Salah is to bring the curtain down on his illustrious career with Liverpool at the end of the 2025-26 season.
"The forward has reached an agreement with the Reds that will see him close a remarkable nine-year chapter at Anfield."
Salah was forced off at Anfield last week after scoring in Liverpool's 4-0 victory against Galatasaray, which sealed their place in the Champions League quarter-finals.
Injury meant he missed fifth-placed Liverpool's 2-1 loss at Brighton last weekend.
Former Liverpool defender Jamie Carragher, in a column for the Daily Telegraph, said Salah would aim to leave in style with victory in the Champions League final.
"Knowing Salah's mindset and competitive spirit, he will be setting his sights on the greatest of all possible goodbyes, inspiring his team to victory in the Champions League final in Budapest," said Carragher.
"Do not bet against the perfect send-off."
