The Sydney-based couple announced the birth of their first child Marlie-Mae Rose Johnson on social media Jun. 20.
"Welcome to the world you divine little slice of human pudding," Byrne shared on Instagram, along with four adorable baby photos. "Marlie-Mae Rose Johnson (named after our Nana's) you're more than we could have ever hoped for."
The 33-year-old jewellery designer ended her post with their daughter's birth date "19.6.19".
New dad Johnson shared an equally excited Instagram announcement, plus two more baby pics.
"Still letting the last 24hrs sink in.. they've been the most rewarding, loving and emotional I've ever experienced," the 31-year-old posted. "@ladyandacat you did the most incredible job bringing our little girl Marlie-Mae Rose Johnson into the world. Becoming a Dad was better than I ever could have imagined."
Other Bachelor Australia alums quickly chimed in with their congratulations for the pair, who met on season 5 of the reality series in 2017.
"She is so perfect and I'm feeling all the feels and I'm so happy for you and so proud!!!" Florence Moerenhout commented.
Alex Nation wrote, "Omg! Congrats you two. Marlie-Mae is perfect," while Jarrod Woodgate added, "She is absolutely beautiful! My heart is melting! Congratulations to the three of you."
Byrne, who has kept fans updated during her pregnancy journey, recently shared what it was like waiting to give birth two weeks after the due date.
"I have sincerely really loved being pregnant. Except for this last week, it's been farrrked. Pretty sure I'm giving birth to a toddler - 41+3," she joked on Instagram on Tuesday.
The reality TV couple, who previously suffered a heartbreaking miscarriage in June 2018, announced they were expecting in December.
"Old mate @matthewdavidjohnson and I are beyond excited to finally be able to share that I'm cooking an orange sized baby Johnson-Byrne," Byrne shared at 15 weeks pregnant. "Happy doesn't even come close."
In April, the pair announced their engagement after Johnson popped the question while on holidays in Fiji.
Congratulations to the happy couple!