The invention provides seed and plants of the lettuce line designated SV3673LD. The invention thus relates to the plants, seeds and tissue cultures of lettuce line SV3673LD, and to methods for producing a lettuce plant produced by crossing a plant of lettuce line SV3673LD with itself or with another lettuce plant, such as a plant of another line. The invention further relates to seeds and plants produced by such crossing. The invention further relates to parts of a plant of lettuce line SV3673LD, including the gametes of such plants.