Faked text messages to keep Brooke Logan away from her father 
Blackmailed Bill Spencer into returning Forrester Creations 
Sabotaged Hope Logan's fashion show by making a sign read "HO for the Future" 
Blackmailed Brooke Logan and Oliver Jones 
Seduced Liam Spencer away from Hope Logan and manipulated him into marriage 
Worked with brother Thomas Forrester to keep Liam from seeing Hope in Cabo San Lucas 
Got into a chocolate fight with Hope Logan 
Tried to seduce Liam Spencer away from Ivy Forrester 
Nearly arrested for violating a restraining order filed by Ivy Forrester 
Slapped Quinn Fuller to the ground 
Steffy Forrester is the daughter of Ridge Forrester and Taylor Hayes; Steffy and her identical twin sister, Phoebe Forrester, were born after Taylor suffered through tuberculosis during pregnancy. Steffy was named for her grandmother, Stephanie Forrester. During a boat trip in St. Thomas, two-year-old Steffy fell overboard and was presumed dead in a shark attack, but Morgan DeWitt, a deranged woman who once was forced to abort Ridge's baby, had kidnapped Steffy and dyed her hair red to pass Steffy off as her daughter. Steffy was rescued when Ridge crashed through Morgan's house in his car.
Steffy was devastated when Taylor died in an altercation with the nefarious Sheila Carter; Steffy was partially raised by Brooke Logan, whom Ridge remarried. Steffy reunited with her parents when it was revealed that Taylor's "body" had been replaced with a dummy by Taylor's former husband, Prince Omar of Morocco, who was keeping Taylor at his palace. Steffy and Phoebe went to London to attend boarding school; while Phoebe returned to Los Angeles, Steffy remained overseas.
Now said to be Phoebe's fraternal twin, Steffy came home from college and worked in the mail room of her family's design house, Forrester Creations, where Steffy met Marcus Walton. Steffy dated Marcus, but gently turned down his proposal after becoming interested in Rick Forrester, who had been involved with both Steffy's mother and sister. Though Steffy initially railed at Rick for his womanizing and blamed him for the car accident which claimed a confrontational Phoebe, Steffy bonded with Rick in her grief, raising the ire of her entire family.
After Steffy agreed to marry Rick, Ridge played her a recording in which Rick admitted he was only romancing Steffy to get back at longtime rival Ridge. Steffy forgave Rick but ultimately let him go because of the dissension their relationship caused within her family. Steffy later turned down Marcus' attempt at a reunion.
To ensure that Ridge and Taylor remarried, Steffy and her brother, Thomas Forrester, faked text messages from Brooke, but Steffy was exposed when Brooke stopped the wedding. Steffy made moves on the married Owen Knight, then developed an attraction to the equally married Bill Spencer, Jr. Steffy kissed Bill before his wedding to Brooke's sister, Katie Logan, whom Bill made CEO of Forrester after he took over the company; Steffy attempted to seduce Bill and swiped Katie's engagement ring, saying she would go to Katie if Bill didn't sign Forrester over to her. Steffy edged out "the Logans"ť by dividing the company's stock between her grandfather Eric Forrester, Stephanie, Ridge, and Taylor.
Steffy worked against Hope Logan by trying to steal her boyfriend, Oliver Jones, and publicly embarrassing Hope by making her "Hope for the Future" sign read "HO for the Future" during a fashion show. Steffy didn't get the chance to publicize Oliver's footage of Bridget Forrester sleeping with the married Owen, but Steffy was able to strike out at Brooke when Brooke mistakenly cheated on Ridge with Oliver at Hope's costumed graduation party. Steffy's attempt to blackmail Brooke and Oliver was defused by Brooke, who confessed to Ridge. Steffy was forced to assemble a video tribute to Brooke, but computer tech Liam Cooper accidentally recorded Steffy talking about Brooke's betrayal; Steffy was blamed when her words were dubbed onto her video by Bill's right-hand man Justin Barber and leaked online.
Angry with Ridge, Steffy contemplated selling Bill the 25% share of Forrester given to her by Taylor. Instead, after a failed attempt to entice Liam away from Hope, Steffy transferred to Forrester International. Coming home with Bill on her mind, Steffy saved Amber Moore when Bill plotted to kill Amber for trapping Liam with a pregnancy. Steffy begged Bill for help when Thomas was lost at sea; Steffy and Bill became closer through the ordeal, but Steffy was distraught that Bill wouldn't leave Katie for her.
Steffy and Bill nearly made love, but Taylor caught them and told Katie. Heartbroken when Bill went back on his promise to leave Katie, Steffy slipped and nearly drowned in a bathtub until she was rescued by Liam. Steffy let Liam know she was sexually available, unlike Hope, who wanted to remain a virgin until her wedding night. Steffy was thrilled when Liam gave her the engagement ring Hope left behind after catching Steffy and Liam kissing; Steffy worked with Bill to keep Liam and Hope apart, spiriting Liam away to Aspen and marrying him while Hope was forced to watch their wedding from a gondola.
Steffy and Liam vacationed at the same resort as Thomas and Hope; Steffy tried to keep Liam from seeing Hope, which led to Steffy being thrown from an ATV. Steffy was diagnosed with a blood clot in her brain that was said to be life-threatening under stress; after it was revealed that Bill faked Steffy's MRI to keep her and Liam together, Steffy held out for a proper divorce from Liam instead of granting him an annulment. Steffy debuted a ski line in Aspen, where Hope, hopped up on antianxiety pills, crashed into Steffy on the slopes. When Liam stayed by Steffy's side in the hospital, Steffy signed Liam's annulment papers, which he tore up.
Steffy grudgingly travelled to Puglia, Italy, for Liam and Hope's wedding; when Hope was a no-show, Steffy welcomed Liam's surprise kiss, but was disappointed when Liam married Hope anyway. Steffy watched the wedding from a distance and fell into the Adriatic Sea. After Hope saw a video of Steffy and Liam kissing and demanded a "do-over" wedding, Steffy took Liam out partying the night before. Once Hope left Liam at the altar for showing up with dyed hair and a tattoo, Steffy informed Liam she would be there for him, and they went parasailing in Aspen.
Steffy spied Liam and Hope kissing; finding out she was pregnant, Steffy refused to tell Liam, giving him time to decide between her and Hope instead. But when Steffy got wind of Liam and Hope's surprise wedding, Steffy stopped it with news of her pregnancy. Steffy rode up the aisle of her own wedding to Liam on a motorcycle; though Liam asked her not to ride again until after the baby was born, Steffy risked it and took a spill that caused her to miscarry. Steffy told unlikely confidante Katie that a botched D&C procedure had left her sterile, then divorced Liam and moved to Paris. Later, Steffy underwent a procedure that restored her fertility and told Liam about it on his wedding day to Hope at the urging of Quinn Fuller, whose son, Wyatt Fuller, wanted Hope for herself. Steffy settled in France after Liam said his heart was with Hope.When Liam came to her begging her to help oust tyrannical Forrester CEO Rick, Steffy announced she would only contribute her 25% share in the company if Liam ditched his current girlfriend, Ivy Forrester, making her point in a bikini. Liam refused, but Steffy later combined her stocks with Ridge, Thomas, and Bill after Ridge told her not to make Liam's return a condition in their takeover plan. Though furious when Liam married the Australian Ivy to keep her in the country, Steffy finally got her chance to reunite with Liam, drawing the ire of young Aly Forrester, whose mother, Darla Einstein, had died falling into the path of Taylor's car. Steffy defended herself against Aly's accusations of promiscuity and implored the increasingly unstable Aly to accept Ridge's California Freedom line, which featured bikinis, lingerie, and transgender models.
After a successful showing, Steffy's car got a flat on the same stretch of highway where Darla died. When Aly nearly ran Steffy down and came at her with a tire iron, Steffy grabbed it and swung at Aly, who hit her head on a rock and died. Steffy stashed the tire iron in the bushes but was horrified when Ivy presented a video in which it looked like Steffy had killed Aly and demanded to be made the New Face of Forrester. After Wyatt got Ivy to delete the incriminating clip, Steffy avenged herself by making the conservative Ivy model lingerie until Liam brokered peace between the cousins. It didn't last long: Steffy found out Ivy had been kissing Thomas behind Wyatt's back and torpedoed their relationship; Steffy's confrontations ended with Ivy getting electrocuted by live wires and falling down the stairs.
Steffy's engagement to Liam hit the skids when she violated Ivy's restraining order; after a series of miscommunications while Liam escorted Ivy onto her plane to Sydney, Steffy allowed herself to be comforted by Wyatt and fell asleep with him in bed. Steffy didn't know that Liam had seen them and couldn't understand his dumping her; with Liam out of town and sending dismissive texts, Steffy began spending time with Wyatt. Before accepting Wyatt's proposal, Steffy talked to Hope and Ivy to see if they'd heard from Liam, which they hadn't. Steffy married Wyatt on the beach and got the shock of her life when a disheveled Liam appeared, having been held captive by Quinn while suffering from amnesia.
It disturbed Steffy to learn that Quinn had Liam believing they were man and wife, and that they'd slept together. Though Liam actively campaigned to win Steffy back, Steffy was inclined to honor her marriage to Wyatt. When the fugitive Quinn showed up asking Steffy to speak to Liam on her behalf, Steffy secretly texted Wyatt to call the police and kept Quinn talking until officers arrived. With Quinn free because Liam's lawyer advised him not to prosecute, Steffy told Wyatt to keep Quinn away from her and her family. However, when Steffy attended the Spencer Summit in Monte Carlo as the face of Spencer's social media, Steffy was outraged to find Quinn romancing Eric and slapped her to the ground. After Eric moved Quinn into Forrester and the mansion, Steffy bunked with Thomas once her threat to leave Wyatt if Quinn didn't walk away backfired.