Abstract: The present invention relates to a Lactuca sativa seed designated 45-101 RZ, which may exhibit a combination of traits including resistance to downy mildew (Bremia lactucae) races Bl:1 to Bl:31 and CA-I to CA-VIII, currant lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, lettuce mosaic virus (LMV), as well as having a medium head size, large outer leaves, and dull to moderately glossy leaves. The present invention also relates to a Lactuca sativa plant produced by growing the 45-101 RZ seed. The invention further relates to methods for producing the lettuce cultivar, represented by lettuce variety 45-101 RZ.