The Manchester City midfielder, goalkeeper Bernd Leno, forward Nils Petersen and defender Jonathan Tah were the four players that failed to make the cut from Loew's provisional list.
Sane, who joined the English champions in 2016, had been a surprise addition to Germany's Euro 2016 squad two years ago but this time he was overlooked by Loew, who opted to take the more physical Julian Brandt to Russia instead.
"It was a very tight decision between him and Julian Brandt which went in favour of Brandt," Loew said. "There are better days in the life of a national team coach, when you have to send four amazing players, who deserve to be at the World Cup, home.
"It's like being at the airport check-in counter en route to Moscow and you are not allowed to board the plane."
Germany captain Neuer, who won the World Cup four years ago, will also be their first choice keeper for the tournament, ahead of designated number two Marc-Andre ter Stegen and Kevin Trapp.
"The clinical tests were really good," Neuer told reporters.
"I always had the goal in front of me. I stayed positive through the injury and had I not been positive I would not have been included.
"I feel good and now my focus is on the World Cup."
Loew announced his squad at the end of a training camp at the Italian Alps. The Germans play their last warm-up game against Saudi Arabia in Leverkusen on Friday before the start of the tournament on June 14.
Germany are in Group F along with Sweden, Mexico and South Korea.
Squad:
Goalkeepers: Manuel Neuer (Bayern Munich), Marc-Andre ter Stegen (Barcelona), Kevin Trapp (Paris St Germain).
Defenders: Jerome Boateng (Bayern Munich), Matthias Ginter (Borussia Moenchengladbach), Jonas Hector (Cologne), Mats Hummels (Bayern Munich), Joshua Kimmich (Bayern Munich), Marvin Plattenhardt (Hertha Berlin), Antonio Ruediger (Chelsea), Niklas Suele (Bayern Munich).
Midfielders: Julian Brandt (Bayer Leverkusen), Julian Draxler (Paris St Germain), Leon Goretzka (Schalke 04), Ilkay Gundogan (Manchester City), Sami Khedira (Juventus), Toni Kroos (Real Madrid), Thomas Mueller (Bayern Munich), Marco Reus (Borussia Dortmund), Sebastian Rudy (Bayern Munich), Mesut Ozil (Arsenal).
Forwards:
Mario Gomez (VfB Stuttgart), Timo Werner (RB Leipzig).
(Reporting by Karolos Grohmann; Editing by John O'Brien)
