While the drama has seen various deaths over the past three series, that hasn't stopped those characters reappearing in future series as hallucinations or flashbacks, so with that in mind, here's who you can expect to see in 13 Reasons Why's final season.
**WARNING: SPOILERS FOR SEASONS 1, 2 and 3 BELOW**
Dylan Minnette plays Clay Jensen
Who is Clay? Clay has come a long way since season one – from uncovering why Hannah Baker killed herself and the horrific crimes committed by Bryce Walker, to throwing Tyler's guns in the ocean and helping to frame Monty for Bryce's murder.
In season four, Clay's guilt from his actions over the past three seasons starts to place the ultimate strain on his mental health, as he worries about Winston revealing the truth about Bryce's death and incriminating all the Liberty High gang.
Where have I seen Dylan Minnette before? 23-year-old Minnette previously made recurring appearances in Lost, Prison Break and Saving Grace and landed roles in Let Me In, Alexander and the Terrible, Horrible, No Good, Very Bad Day and horror film Don't Breathe. He recently starred in Netflix's thriller The Open House.
Brandon Flynn plays Justin Foley
Who is Justin? Popular jock Justin Foley was the very first person to be mentioned in Hannah Baker's tapes in season one, and since then he's developed a heroin addiction and been adopted by Clay's parents after finding himself homeless.
Will Justin finally be able to win his battle with substance abuse in the final series? And can his relationship with Jessica progress despite the pain he's inflicted on her in the past?
Where have I seen Brandon Flynn before? Justin is played by Brandon Flynn, who prior to 13 Reasons Why, appeared in political satire BrainDead and season three of True Detective.
Alisha Boe plays Jessica Davis
Who is Jessica? The last time we saw Jessica Davis, the Student Body President was coming to terms with being a survivor of sexual assault and covering up Bryce's murder after witnessing his death.
Will Jessica be able to prevent Clay from unravelling in the presence of Winston? And has she completely made peace with Justin's part in Bryce's rape of her?
Where have I seen Alisha Boe before? Norway-born actress Boe began her acting career by starring in horror films Amusement and Paranormal Activity 4 before appearing in Parenthood, Modern Family, soap Days of Our Lives and Ray Donovan. She recently acted alongside Stranger Things' Natalia Dyer in comedy Yes, God, Yes.
Christian Navarro plays Tony Padilla
Who is Tony? Tony became a suspect in Bryce's murder last season after it was revealed that Bryce's father had Tony's father deported to Mexico. Season four will likely see Tony try to bring his family back to the US and retrieve his sister, who he had to send to live with relatives in Arizona.
Where have I seen Christian Navarro before? 28-year-old Navarro, who plays Tony Padilla, was born and raised in New York and has since appeared in The Affair and the HBO drama Vinyl. He recently played a minor role in Oscar-nominated film Can You Ever Forgive Me?
Miles Heizer plays Alex Standall
Who is Alex? Alex's mental health has deteriorated since the release of Hannah Baker's tapes, with his suicide attempt at the end of season one to his killing of Bryce last season.
Although his police officer father covered his tracks and blamed Monty for Bryce's murder, will Alex be able to live with his guilt? And will Monty's ex Winston reveal the truth?
Where have I seen Miles Heizer before? Kentucky-born Heizer has played Alex in 13 Reasons Why since the show began in 2017. He previously starred in Parenthood as Drew Holt and appeared in films Love Simon, Nerve and The Stanford Prison Experiment.
Ross Butler plays Zach Dempsey
Who is Zach? Zach, revealed to be Hannah Baker's ex-boyfriend, had his football career ruined after a fight with Bryce busted his knee and played a role in covering up Alex's murder of Bryce.
Season four will see Zach develop in an unexpected direction this series – how will he cope with the deaths of his former friends Bryce and Monty?
Where have I seen Ross Butler before? 30-year-old Butler originally played Reggie Mantle in Riverdale but was replaced by Charles Melton after joining the cast of 13 Reasons Why. Butler previously appeared in Disney's K.C. Undercover, and more recently starred in To All The Boys: P.S I Still Love You and superhero film Shazam.
Devin Druid plays Tyler Down
Who is Tyler? School photographer (and Hannah Baker's former stalker) Tyler Down spent season three in a dark place after being brutally assaulted by Monty de la Cruz and attempting a school shooting, which was stopped by Clay.
Although Clay and Tony covered for Tyler by throwing his guns in the ocean, will his school shooting attempt come back to haunt him this season?
Where have I seen Devin Druid before? 22-year-old Devin made his screen debut in 2012 documentary Trading Ages and has since appeared in Louie, Olive Kitteridge, House of Cards and horror film Cam.
Justin Prentice plays Bryce Walker
Who is Bryce? Although serial rapist Bryce Walker was killed during season three, in the upcoming series it looks like he'll be back to haunt his former friends, who covered up his murder.
Where have I seen Justin Prentice before? 26-year-old Prentice was a main cast member in sitcom Malibu Country before appearing in Glee, iZombie, Awkward and Preacher.
Timothy Granderos plays Monty de la Cruz
Who is Monty? Last season, Monty de la Cruz died in prison after being jailed for raping Tyler but in the upcoming season he'll be appearing in Clay's hallucinations as he deals with the guilt of framing Monty for Bryce's murder.
Where have I seen Timothy Granaderos before? Granaderos previously appeared in Fall Out Boy's music video for their single Champion and Marvel's Runaways.
Grace Saif plays Ani Achola
Who is Ani? British Ani Achola was introduced as a new character (and controversially, the narrator) in season three, quickly becoming romantically involved with Bryce and Clay and investigating Bryce's murder.
Will we be seeing season four from her perspective again? And will her role in Monty's framing be uncovered by Winston?
Where have I seen Grace Saif before? Recent Royal Academy of Dramatic Arts graduate Grace Saif landed her first major role in 13 Reasons Why as new character Ani. She previously appeared in an episode of Doctors and various London theatre productions.
Deaken Bluman plays Winston Williams
Who is Winston? Monty's secret ex-boyfriend Winston revealed last season that he was with Monty the night of Bryce's murder and therefore knows that Monty was framed.
Season four will see Winston snoop around Liberty High in an attempt to dig deeper into Bryce's murder. What does he have planned for the group and will he reveal the truth?
Where have I seen Deaken Bluman before? Winston Williams is one of actor Bluman's first big roles, having previously appeared in TV series First Love and a series of short films.
Jan Luis Castellanos plays Diego Torres
Who is Diego? Season four will see the introduction of new character Diego Torres, a friend of the late Monty who is struggling to deal with his loss. Will he be teaming up with Winston to uncover the truth about Monty being framed?
Where have I seen Jan Luis Castellanos before? Castellanos is a 22-year-old actor from the Dominican Republic, who recently appeared in Marvel's Runaways as Topher.
Gary Sinise plays Dr Robert Ellman
Who is Dr Robert Ellman? Dr Robert Ellman will be introduced as the Jensen family's therapist during 13 Reason's Why's final season. Will he be able to draw the truth out of Clay?
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Where have I seen Gary Sinise before? Dr Ellman is portrayed by award-winning actor Gary Sinise, who has starred in various Hollywood blockbusters including Forrest Gump, The Green Mile and Apollo 13, and starred in the TV series CSI: NY. He recently appeared in Captain America: The Winter Soldier and Criminal Minds spin-off Beyond Borders.
Who else stars in 13 Reasons Why season 4?
Josh Hamilton and Amy Hargreaves will be reprising their roles as Clay's parents Matt and Lainie Jensen this series, but it's currently unknown whether Katherine Langford will appear again as Clay's hallucination of Hannah Baker.
The final season of 13 Reasons Why lands on Netflix on Friday 5th June – check out our list of the best TV shows on Netflix and the best movies on Netflix, or see what else is on with our TV Guide