It was clear from Lambert's face after he scored just how much it had meant to him to reach the mark.
He said: "It was very special, very special. I knew what I was on, and it means a lot getting 100 goals for Southampton.
"It's something I'm very proud of.
"It has been the best four-and-a-half years of my life," he added. "I have given everything and I will carry on giving everything I can while I am here. I have absolutely loved it."