LIM domain transcription factor LMO4 is a protein that in humans is encoded by the LMO4 gene.

LIM domain only 4 is a cysteine-rich, two LIM domain-containing protein that may play a role as a transcriptional regulator or possibly an oncogene. Its mRNA is characterized by a GC-rich 5' region and by multiple ATTT motifs in the 3' region. A variant transcript missing a portion of the 5' region has been identified but cannot be confirmed because of the GC-rich nature of the region.

LMO4 has garnered significant attention for its involvement in cancer, particularly breast cancer. It is overexpressed in a substantial percentage of primary breast carcinomas. Studies have shown that LMO4 can promote the proliferation of mammary epithelial cells, inhibit their differentiation, and enhance cell invasion and motility, all of which are hallmarks of cancer progression.

LMO4 has been shown to interact with LDB1, RBBP8 and BRCA1.