WASHINGTON (REUTERS) - United States Special Counsel Robert Mueller has submitted his report on the investigation of whether Mr Donald Trump's 2016 campaign conspired with Russia and whether the President unlawfully tried to obstruct the inquiry.
Attorney General William Barr issued a summary of the report on Sunday (March 24), saying Mr Mueller found no evidence that any member of Mr Trump's election campaign conspired with Russia during the election.
Below are some key figures in the investigation.
DONALD TRUMP JR
Mr Trump's eldest son set up a June 2016 meeting at Trump Tower in New York with a Kremlin-linked lawyer, Ms Natalia Veselnitskaya, and other Russians who had offered damaging information on election rival Hillary Clinton.
In an e-mail after being promised the Clinton "dirt", Mr Trump Jr wrote "I love it".
When news of the meeting broke in July 2017, Mr Trump Jr issued a statement saying the meeting was set up to discuss adoption policy, not politics, before later admitting he had been expecting intelligence on Mrs Clinton.
President Trump's advisers eventually said the President dictated the misleading statement put out in his son's name, after initially denying his involvement.
Mr Trump's son-in-law has served as a senior adviser to him as both candidate and president.
Mr Kushner initially did not list any Russian contacts on his application for a White House security clearance, but subsequently revised those forms to reveal he had participated in the June 2016 Trump Tower meeting and discussed setting up a secure communications line at the Russian Embassy in Washington after Mr Trump won the November 2016 election with Mr Sergei Kislyak, then-Russian ambassador to the US.
Mr Sessions, a longtime senator from Alabama, served as a campaign adviser and then Mr Trump's first attorney general.
During his Senate confirmation hearings, he said he did not meet Russian officials during the campaign, but later admitted he had met Mr Kislyak at least twice.
Under pressure, Mr Sessions recused himself from oversight of the Russia investigation, which at the time was led by the FBI and later by Mr Mueller. The recusal angered Mr Trump, who eventually fired him last November.
A retired US Army lieutenant general, Flynn was a top campaign adviser and served as Mr Trump's first national security adviser until he was fired after only weeks on the job for lying about his conversations with Mr Kislyak in December 2017, after Mr Trump won the election but before he took office.
Flynn discussed US sanctions with Russia and asked the ambassador for help with a United Nations vote, according to court filings. Flynn pleaded guilty to lying to the FBI and has been cooperating with investigators.
Before he joined Mr Trump's campaign, Flynn sat next to Russian President Vladimir Putin at a Moscow dinner in December 2015 celebrating RT, a pro-Kremlin Russian-owned English language media channel.
Manafort served on Mr Trump's campaign from March to August 2016, including three months as chairman, ensuring Mr Trump secured the Republican presidential nomination during the party's convention in Cleveland. During that time, the Republican Party softened its support for arming US allies in Ukraine.
He participated in the Trump Tower meeting with Russians who offered damaging information on Mrs Clinton.
Manafort's lawyers said that after the convention, he shared election polling data and discussed a way to end the Ukraine conflict with Russian Konstantin Kilimnik, a former business associate who Mr Mueller's team has called an agent of the Kremlin.
Manafort was sentenced to 7½ years in prison on March 13 in two cases prosecuted by Mueller. He was found guilty in Virginia of bank and tax fraud related to millions of dollars he earned as a political consultant for pro-Russian politicians in Ukraine.
He pleaded guilty in Washington to two conspiracy charges. A judge ruled on Feb 13 that Manafort violated his plea agreement with prosecutors by repeatedly lying to Mr Mueller's team.
Less than an hour following his sentencing, the former campaign chairman was charged with residential mortgage fraud and other felonies in New York. State lawmakers moved to ensure Manafort can be prosecuted even if he receives a presidential pardon.
Manafort's longtime lobbying associate served as deputy campaign chairman and worked on the transition after Mr Trump was elected.
Gates pleaded guilty to lying to investigators and was a star witness in Manafort's 2018 trial, testifying that he helped his boss file false tax returns and hide millions of dollars offshore.
Gates has continued to cooperate with the investigation, according to court filings.
Mr Trump's former longtime personal attorney once boasted that he would take a bullet for his boss, but has since turned on him.
In a series of guilty pleas, Cohen said he worked on a deal to build a Trump tower in Moscow for nearly a year while Mr Trump was running for president, and acted at Mr Trump's direction to break campaign-finance laws by arranging "hush money" payments to women who claim to have had sexual relationships with Mr Trump.
Cohen's turn against Mr Trump was on dramatic display in his congressional testimony on Feb 27, accusing the President of being a "racist", "conman" and "cheat". Cohen is due to begin serving a three-year prison sentence on May 6.
Stone is a self-proclaimed political "dirty trickster" who has known Mr Trump for about four decades. He is accused of telling members of Mr Trump's presidential campaign that he knew in advance of plans by the WikiLeaks website to release damaging e-mails about Mrs Clinton.
Cohen has said he heard Stone tell Mr Trump on the telephone in July 2016 about a forthcoming release by WikiLeaks of the stolen e-mails.
US intelligence agencies have concluded the e-mails were stolen by Russians. They sowed division among Democratic voters by showing that Democratic Party officials had favored Mrs Clinton over insurgent candidate Bernie Sanders. Stone pleaded not guilty in January to charges brought by Mr Mueller.
INTERNET RESEARCH AGENCY
Mr Muller's team has said this St Petersburg-based organisation tried to influence the 2016 US presidential election through fake social-media accounts, aiming to spread distrust about the candidates and the American political system.
The organisation employed hundreds of people, according to an indictment.
The former New York mayor and 2008 Republican presidential candidate has offered a freewheeling defence of the President in the news media since signing on as Mr Trump's personal lawyer in April 2018.
Mr Giuliani has occasionally misstated facts, drawing rebukes from Mr Trump or other members of his administration.
This Russian woman, a former graduate student at American University in Washington, has admitted to trying to infiltrate the influential National Rifle Association lobby group and make inroads with conservative activists and Republicans as an agent for Moscow in a criminal case in parallel with the Mueller investigation.
Butina pleaded guilty to a conspiracy charge in December 2018 and has agreed to cooperate with US investigators.
As FBI director, Mr Comey oversaw the initial stages of the Russia investigation until Mr Trump fired him in May 2017.
The White House initially said Mr Comey was fired because he had mishandled a 2016 investigation into Mrs Clinton's e-mails, but shortly thereafter, Mr Trump told NBC that he had "this Russia thing" on his mind in the dismissal. Mr Comey has said that Mr Trump pressured him to end the investigation of Flynn.
The Trump foreign-policy adviser met Russian officials in Moscow in July 2016, and has said he reported back to Mr Sessions and other senior campaign officials after the trip.
His contacts attracted suspicion from the FBI, which said in surveillance applications that it believed Mr Page "has been collaborating and conspiring with the Russian government" and had established relationships with Russian intelligence officers.
Mr Page, who has not been charged, has said he did nothing wrong.