《One》是韩国民谣女歌手李秀英（이지연）演唱的一首歌曲。同时，此曲也是游戏《RF Online》的主题曲。
《RF Online》是一款由韩国CCR公司开发，广东数据通信于2005年12月15日运营的网络游戏。游戏讲述了玩家扮演的三大种族（阿克雷提亚、贝尔托、克拉）之间的反目与对立，以及和神秘病毒斗争的故事。
One歌词：
When I saw you for the first time
I knew you were the one
You didn't say a word to me
But love was in the air
Then you held my hand
Pulled me into your world
From then on my life
Has changed for me
Now I'll never feel lonely again
Coz you are in my life
Love
How can I explain to you
The way I feel inside when I think of you
I thank you for everything that you showed me
Don't you ever forget that I love you
Love I know that someday real soon
You'll be right next to me
Holding me so tight
So I will always be yours
Although we can't be together now
Remember I am here for you
And I know you're there for me
Whenever I want to be with you
I just close my eyes and pretend you're near
I see you I touch you I feel you like real
Nothing can ever change what I feel inside
How long must I be far away from you
I don't know dear but I know we are one
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