On January 3, 2018, Cardi B was featured on Bruno Mars' remix version of "Finesse", and also appeared in the 90s inspired video. It reached the top three on the Hot 100, Canada and New Zealand. On January 18, 2018, Cardi B became the first woman to have five top 10 singles simultaneously on the Billboard Hot R&B/Hip-Hop Songs chart. She released another single, "Be Careful", on March 30, 2018, a week before her album's release.
Her debut studio album, Invasion of Privacy, was released on April 6, 2018, to universal acclaim from music critics. Editors from Variety and The New York Times called it "one of the most powerful debuts of this millennium" and "a hip-hop album that doesn't sound like any of its temporal peers," respectively. The album entered at number one in the United States, while she became the first female artist to chart 13 entries simultaneously on the Billboard Hot 100, on the chart issue dated April 21. It also became the most streamed album by a female artist in a single week in Apple Music, and the largest on-demand audio streaming week ever for an album by a woman. Cardi held the latter record until 2019. The album's title reflects Cardi B's feeling that as she gained popularity her privacy was being invaded in a variety of ways. Following the album's release, during a performance on Saturday Night Live, Cardi B officially announced her pregnancy, after much media speculation. She also co-hosted an episode of The Tonight Show Starring Jimmy Fallon.
Several months later, in July 2018, the album's fourth single, "I Like It", which features vocals from Bad Bunny and J Balvin, reached number one on the Hot 100; this marked her second number one on the chart and made her the first female rapper to achieve multiple chart-toppers. It received critical acclaim, with Rolling Stone naming it "the best summer song of all time" in 2020. Her collaboration with Maroon 5, "Girls Like You", also reached number one the Hot 100 chart, extending her record among female rappers and also making her the sixth female artist to achieve three number-one singles on the chart during the 2010s. The song's music video has received more than 2.7 billion views on YouTube and was the fifth-best selling song of the year globally. With "Girls Like You" following "I Like It" at the top of the Billboard Radio Songs chart, Cardi B became the first female rapper to ever replace herself at number one on that chart. The single spent seven weeks atop the Hot 100, making Cardi the female rapper with the most cumulative weeks atop the chart, with eleven weeks. It spent 33 weeks in the top 10, tying both Ed Sheeran's "Shape of You" and Post Malone and Swae Lee's "Sunflower" for the longest top 10 run in the chart's archives at the time. In October 2018, Invasion of Privacy was certified double platinum by the RIAA, and the following year it was updated to triple platinum. With the thirteen tracks, she became the first female artist to have all songs from an album certified gold or higher in the US.
On November 30, 2018, Cardi B was honored at Ebony's annual Power 100 Gala. Cardi ranked fifth on the 2018 Billboard Year-End Top Artists chart, while Invasion of Privacy ranked sixth. She achieved the most-streamed album of the year by a female artist globally in Apple Music, and ranked as the most streamed female artist of the year in the United States in Spotify. Editorial staff from Apple Music and Billboard named "I Like It" the best song of 2018, while Time magazine and Rolling Stone named Invasion of Privacy the best album of the year. Also in 2018, Time included her on their annual list of the 100 most influential people in the world. In its decade-end review article, NME stated that the era secured "her crown as the new Queen of Rap."
The star has been called "unabashedly, directly political" and often uses social media to advocate for causes she believes in, such as gun control. During the 2016 presidential primaries, she warned her fans of President Trump's immigration policies and encouraged them to vote for Senator Bernie Sanders. At the Grammy Awards in 2018, she appeared in a video along with Hillary Clinton to narrate a portion of Fire and Fury, Michael Wolff's insider's account of Trump's administration, and stated "Why am I even reading this shit? I can't believe this. I can't believe—this is how he really lives his life?" Cardi B endorsed Sanders once again in his second bid for the presidency in the 2020 United States presidential election, while also praising U.S. Representative Tim Ryan. She also stated that one of the reasons for her endorsement is Sanders' long-time involvement in supporting underprivileged minorities and "people getting Medicare because he knows they can't afford it," while Politico website argued that she "might be one of Bernie's most powerful 2020 allies." She has also used her social pages to raise awareness for victims of police brutality, and has encouraged people to vote for mayors, judges and district attorneys in local elections. In a conversation with Democratic candidate Joe Biden for Elle, they discussed Medicare, free college tuition, and racial equality. According to a study published by The Hollywood Reporter, Cardi B ranked as the fifth most influential celebrity, and fourth among Generation Z, for the 2020 presidential election.
After the release of "Girls" in May 2018, a collaboration where she had a featured verse, Cardi B responded to the accusations of the song trivializing and sexualizing LGBT relationships. She stated on Twitter, "We never try to cause harm or had bad intentions with the song." Cardi B then went on to say, "I personally myself had experiences with other women."
Cardi has a noted affinity for Christian Louboutin heels, a running theme in her song "Bodak Yellow". She has also mentioned her affinity for cheap, fast-fashion brands stating "I don't care if it cost $20 or $15. If it looks good on me, it looks good on me". In November 2018 she released a collection with Fashion Nova. Cardi wore vintage Thierry Mugler to the 2018 Grammy Awards. An article from Vogue noted she "is famous for her statement getups—whether she's rocking archival Mugler on the red carpet, or dripping in Chanel while sitting courtside at a basketball game." Her over-the-top manicures, designed by nail artist Jenny Bui and studded with Swarovski crystals, has become a part of her signature look.
In 2018, she became the first female rapper in the US to appear on the cover of Vogue. Photographed by Annie Leibovitz, the cover, one of four for the January 2019 issue that included Stella McCartney, features her in a red and white Michael Kors dress and matching red Jimmy Choo shoes, while holding her daughter, Kulture.
Cardi B is the recipient of numerous accolades, including a Grammy Award, eight Billboard Music Awards, five Guinness World Records, four American Music Awards, four MTV Video Music Awards, four BET Awards, and eleven BET Hip Hop Awards. Time included her on their annual list of the 100 most influential people in the world in 2018. She received the ASCAP award for Songwriter of the Year in 2019, becoming the first female rapper to win the award. She received the honor for the second time in 2020, making her the first female songwriter to win the award twice.
In an interview in 2018, Cardi talked about being Afro-Latina and Afro-Caribbean:
As of early 2017, Cardi B began publicly dating fellow American rapper Offset, of the southern hip hop group Migos. When speaking on her relationship with Offset, Cardi B told The Fader, "It's been a blessing, me meeting him and meeting his friends. I see how hard they work. And that motivated me to work even harder. And I see how good things are going for them and how popping it is to be number one. And I'm like, I want that. A lot of people just see they jewelry and they money, but I don't think a lot of people see how hard they work for that shit every single day." Cardi B and Offset became engaged on October 27, after Offset proposed to Cardi B at the Wells Fargo Center in Philadelphia, during the Power 99 Powerhouse concert. On April 7, 2018, Cardi B revealed that she was pregnant with Offset's child on Saturday Night Live. On June 25, 2018, TMZ found a marriage license revealing Cardi B and Offset had secretly married in September 2017 privately in their bedroom. Cardi B later went on to confirm this revelation in a social media post. In July 2018, Cardi B gave birth to her first child, a daughter named Kulture Kiari Cephus. In December 2018 she announced on Instagram that she and Offset had broken up, though the pair later reunited. In February 2019, the couple made a public appearance for the Grammys. He accompanied her on the stage during her acceptance speech for Best Rap Album. In September 2020, it was reported that Cardi B had filed for divorce, but the next month it was revealed they were back together.
On October 1, 2018, Cardi B agreed to meet with investigators at a Queens police station, in connection with an alleged attack she ordered on two bartenders. Cardi B's denied involvement through her attorney. She was charged with two misdemeanors: assault and reckless endangerment. Cardi B appeared in court for her arraignment on December 7, 2018, after she failed to show up for the originally scheduled date due to a scheduling conflict, according to her attorney. She was ordered by the judge to avoid having any contact with the two bartenders. She was released by the judge despite prosecutors requesting bail to be set at $2,500. On June 21, 2019, a grand jury indicted Cardi B on 14 charges, including two counts of felony assault with intent to cause serious physical injury, stemming from the incident. She was arraigned on June 25, 2019 and pleaded not guilty on all charges.