The star sings on Love Lies from the Love, Simon soundtrack; and has sailed into the Billboard Hot 100 at No43.
That’s reportedly the highest debut for a solo girlband member of all time, according to MTV.
For comparison, Diana Ross made her arrival at No49 in 1970 with Reach Out and Touch (Somebody’s Hand), and Kelly Rowland’s Nelly duet Dilemma made its start at No53.
Beyonce’s 03 Bonnie and Clyde bowed at No56, and I Know What You Did Last Summer – the first solo venture by Normani’s former bandmate Camila Cabello, a duet with Shawn Mendes – arrived at No97 in 2015.
Normani tweeted: “Thank you for giving me the chance. Thank you for your unconditional love and commitment.
“I see you all and I greatly appreciate all that you’re doing in support of my vision. I love you more than I can verbally say.
“I’m forever grateful. You have my heart.”
Love, Simon – a high-school comedy about a young man coming to terms with his sexuality – is due in cinemas on April 6 in the UK.
Normani remains a part of Fifth Harmony, alongside Ally Brooke, Dinah Jane and Lauren Jauregui.
Brooke released a single earlier this year, while Jauregui collaborated with Steve Aoki and Halsey in 2017.
Cabello recently scored a No1 album and single in the US, and will be here on tour in the spring.