Westbrook leaves the Rockets after just one season alongside James Harden in Houston, the nine-time All-Star moving to Washington in exchange for Wall and a future lottery-protected first-round draft pick on Wednesday.
The shock trade comes amid uncertainty over Rockets superstar Harden, who is reportedly eyeing a move to the Brooklyn Nets, while the Philadelphia 76ers have also been linked.
Wall heads to Houston, having not played since rupturing his left Achilles tendon in January last year. He initially underwent season-ending left heel surgery.
The five-time All-Star, who has appeared in just 73 games since the start of the 2017-18 season, is fourth for career points for the Wizards after being drafted first by the Washington franchise in 2010.
"Having the opportunity to acquire a player of Russell's calibre and character was something that we could not pass up when looking at both the immediate and long-term future of our team," said Wizards general manager Tommy Sheppard as Westbrook prepares to team up with Bradley Beal.
"With that said, the decision to part ways with John, one of the greatest players in franchise history, was extremely difficult. What he has meant to our organisation and our community is immeasurable and will not be forgotten."
Harden and Westbrook – who played together at the Oklahoma City Thunder – became the first pair of team-mates in NBA history to average 25.0-plus points and seven-plus assists per game in the same season.
Westbrook averaged 27.2 points and seven assists per game for the Rockets, who had their 14th consecutive season at .500 or better but failed to reach the NBA Finals – the longest streak of its kind in NBA history.
But Westbrook's struggles were evident in the playoffs – shooting just 24.2 per cent from three-point range and 53.1 per cent from the free-throw line.
Westbrook was the first player in NBA history to shoot under 25 per cent from three and under 60 per cent from the line in a single postseason (minimum 30 attempts in both categories).
Houston had a 29-13 record when Westbrook shot less than five times from beyond the arc compared to 10-13 when attempting five or more.
Westbrook, meanwhile, has a career average of 19.6 points, 9.0 assists and 6.1 rebounds in Washington.
Wizards head coach Scott Brooks added: "Russell's accomplishments and honours on the court speak for themselves, but his drive and will to win are what separate him as a truly unique player.
"As much as I'm looking forward to reuniting with him, I'm equally sad to say good-bye to John. He is one of the toughest and most gifted players I've ever been around and we all wish him nothing but the best moving forward."
In 573 career games with 561 starts for the Wizards, Wall averaged 19.0 points, 9.2 assists, 4.3 rebounds, and 1.70 steals. He joins Magic Johnson and Oscar Robertson as the only players in NBA history with career averages of at least 19.0 points per game, 9.0 assists per game and 4.0 rebounds per game.
Over the past six seasons, Wall is the only player in the league to have averaged at least 20.0 points per game and 10.0 assists per game.
In return for Westbrook and second-round picks in 2024 and 2028, the Lakers reportedly are sending Kyle Kuzma, Montrezl Harrell, Kentavious Caldwell-Pope and the 22nd overall pick in Thursday's draft to Washington.
While the deal cannot be officially completed until August 6, when the salary cap for next season is set, commissioner Adam Silver announced the portion involving the draft pick from the podium on Thursday.
With the 22nd pick that was part of the trade, the Lakers selected Isaiah Jackson from Kentucky and sent him to Indiana as part of a separate deal between the Indiana Pacers and Wizards that reportedly will net Washington Aaron Holiday and the number 31 pick.
But Los Angeles native and former UCLA star Westbrook was the man everyone was talking about on Thursday.
After one season with Washington, Westbrook will head west to join LeBron James, Anthony Davis and the Lakers as they try to bounce back from a first-round playoff loss a year after winning the NBA title.
The move will cost LA, who will owe their new star trio a combined $121million next season.
But the Lakers will be hoping for big things from the nine-time All-Star Westbrook, who was the league's MVP in 2016-17 while playing for the Oklahoma City Thunder and turns 33 in November.
Westbrook averaged 22.2 points and a career-high 11.7 assists and 11.5 rebounds in 65 regular-season games last season, recording triple-doubles in 38 of them.
Along the way, he broke Oscar Robertson's long-standing record of 181 career triple-doubles, finishing the season with 184.
From Washington's perspective, moving on from Westbrook frees up money to keep Bradley Beal as the team's centerpiece moving forward as he enters the final year of his contract.
The Wizards also added some supporting pieces in the deal, as Harrell averaged 13.5 points and 6.2 rebounds for the Lakers last season, while Kuzma contributed 12.9 points and 6.1 rebounds and Caldwell-Pope 9.7 points.
Former NBA MVP Westbrook will play for the Wizards in 2020-21 after being dealt by the Houston Rockets in exchange for John Wall last week.
While Westbrook remains one of the NBA's elite scorers and creators, concerns over his demeanour and character continue to linger after spending just one season with former Oklahoma City Thunder team-mate James Harden in Houston.
But two-time All-Star Beal told reporters on Friday: "I'm not KD [Kevin Durant], I'm not PG [Paul George], I'm not Vic [Oladipo], I'm not James.
"We all maybe have our similarities, but we are all different in our ways. I'm not going to judge Russ off of his previous relationships with guys on other teams. I want to be able to put my foot in his shoes and be in the moment. I want to experience these things for myself."
Westbrook averaged 27.2 points and seven assists per game for the Rockets, who had their 14th consecutive season at .500 or better but failed to reach the NBA Finals – the longest streak of its kind in NBA history.
But Westbrook's struggles were evident in the playoffs – shooting just 24.2 per cent from three-point range and 53.1 per cent from the free-throw line.
Westbrook was the first player in NBA history to shoot under 25 per cent from three and under 60 per cent from the line in a single postseason (minimum 30 attempts in both categories).
Houston had a 29-13 record when Westbrook shot less than five times from beyond the arc compared to 10-13 when attempting five or more.
"He's a great passer," Beal said. "He can pass the hell out of the ball. His pace is crazy. I don't want to just compare him and John, but he's very fast with the ball... and he's looking for his shooters.
"It's definitely cool to see that. I feel like there is always a false narrative on Russ, but he's looking for guys, he's trying to get guys the ball and he's coaching."
Nine-time All-Star Westbrook added: There is no sugarcoating, there is no me trying to be somebody I'm not. Since I have been in this league, I feel like I'm one of the best leaders in the game.
"Leadership is not about what you say and all the s*** that people see, but it's actually what you do and how you impact and better your team-mates as men and people."
Westbrook will be re-evaluated at the end of the week after suffering repeated contact to the area since the start of the NBA season, the Wizards announced on Monday.
It is a blow for the Wizards, who have slumped to 2-8 amid high expectations following Westbrook's arrival from the Houston Rockets.
Former MVP Westbrook is averaging 19.3 points, 11.3 assists and 9.7 rebounds per game in seven appearances for the Wizards this season.
Westbrook has already made some history since swapping the Rockets for the Wizards in a blockbuster trade.
The nine-time All-Star joined Hall of Famer Oscar Robertson as the only players in NBA history to open a season with four triple-doubles in their first four games.
Westbrook scored 41 points on Saturday as the Rockets edged a thrilling game with the Celtics 111-110 at TD Garden.
The win moved the Rockets to 39-20 for the season, with Houston fourth in the Western Conference standings.
"You can't go to the supermarket and buy heart," D'Antoni said of Westbrook. "You know he has that. It's pretty impressive."
Celtics guard Jaylen Brown hit a buzzer-beating three-pointer to send the game to overtime.
However, he conceded the Celtics did not defend well against Westbrook, having held his fellow former MVP, James Harden, to 21 points.
"I think we guarded [Harden] well," Brown said. "I think we accepted his challenge. We just didn't do a good enough job with Westbrook.
"We had a lot of attention on James Harden and forgot about the other MVP over there. He came out and asserted himself early and took over and dominated this game."
The Rockets' decision to trade center Clint Capela in January appears to have had an instrumental impact on Westbrook.
Houston have tweaked their style of play to afford him more opportunities to attack the basket, but Westbrook was non-committal on whether those changes have put him in the best position ever to succeed.
"I don't know, man," Westbrook said. "I just try to find ways every year to be better and find ways to become a better player and team-mate.
"Obviously based on the changes we made and the way we line up, I have to find ways to constantly keep being effective and help my team win games and that's what I try to do.
"Right now, I think I'm moving in the right direction. I've just got to stay locked in on what I'm doing and my craft and keep doing what I've been doing since I've been in the league, and that's going out and competing every night."
Huge expectations surrounded Williamson's long-awaited debut and the number one draft pick did not disappoint at
The 19-year-old, having overcome knee surgery, erupted for 17 straight points in the fourth quarter to finish with a joint team-high 22, plus seven rebounds, through 18 minutes in the New Orleans Pelicans' 121-117 loss to the San Antonio Spurs.
LaMarcus Aldridge led the Spurs with 32 points and 14 rebounds, while DeMar DeRozan added 20 points.
Harden and Westbrook put on their own show in Houston, combining for 55 points as the Rockets topped the Denver Nuggets 121-105.
Fred VanVleet made six of his seven three-point attempts to help the Toronto Raptors prevail 107-95 against the Philadelphia 76ers.
LeBron, Davis drive Lakers
LeBron James dropped 21 points and Anthony Davis had 28 as the Los Angeles Lakers downed the New York Knicks 100-92 at Madison Square Garden.
The win ensured the Lakers bounced back from their heavy loss to the Boston Celtics, who made it two wins on the trot with a 119-95 victory over the Memphis Grizzlies.
There was an overtime thriller in Miami, where Jimmy Butler recorded 24 points, 10 assists and seven rebounds to take the Heat to a 134-129 defeat of the Washington Wizards.
The Los Angeles Clippers' four-game winning streak came to a surprise end against the struggling Atlanta Hawks, who had John Collins to thank for 33 points and 16 rebounds in a 102-95 triumph.
Difficulty for Draymond
Draymond Green struggled on his return from illness as the Golden State Warriors slumped to 129-96 home loss to the Utah Jazz.
The three-time NBA champion played 25 minutes for five points, four rebounds and two assists in the rout.
Zion sends New Orleans into frenzy
Williamson lit up Smoothie King Center, proving a danger from beyond the arc as he went four from four from three-point range.
Wednesday's results
Utah Jazz 129-96 Golden State Warriors
Toronto Raptors 107-95 Philadelphia 76ers
Detroit Pistons 127-106 Sacramento Kings
Oklahoma City Thunder 120-114 Orlando Magic
Los Angeles Lakers 100-92 New York Knicks
Boston Celtics 119-95 Memphis Grizzlies
Miami Heat 134-129 Washington Wizards (OT)
Atlanta Hawks 102-95 Los Angeles Clippers
Chicago Bulls 117-110 Minnesota Timberwolves
Houston Rockets 121-105 Denver Nuggets
Indiana Pacers 112-87 Phoenix Suns
San Antonio Spurs 121-117 New Orleans Pelicans
Lakers at Nets
Kyrie Irving is expected to return from a hamstring problem when the Brooklyn Nets (18-24) host the Lakers (35-9) on Thursday.
