Giudici beat out fellow finalist Lindsay Yenter for the honor.
The season kicked off with 26 women vying for Lowe's affection.
"I think the world of you and I miss you every time we have to say goodbye. I don't want to say goodbye anymore," Lowe told Giudici. "Catherine, I want to spend the rest of my life telling you, 'I love you,' and making you feel like the most special, beautiful woman in the world. Catherine, will you marry me?"
Giudici accepted the 3-carat Neil Lane diamond ring he offered, telling Lowe: "I'm so happy ... I am so grateful to have met somebody like you. I've never been so comfortable about myself and with somebody."