This document is a Request for Proposal (RFP) for the construction of the Near Detector Complex as part of the Fermilab LBNF/DUNE-US Project. The RFP provides instructions to offerors, drawings, specifications, and a sample subcontract for the project. The scope of work includes construction services for a service building, primary and secondary shafts, detector cavern, and site improvements to house and support the LBNF Near Detector. Offerors are required to attend a mandatory pre-proposal conference on July 10, 2024, and submit any questions by August 8, 2024. The proposals shall be valid up to the anticipated award date, which is 7 months from the proposal due date. Fermi Research Alliance (FRA) expects to select one subcontractor to perform the work under a Firm Fixed Price (FFP) subcontract. FRA reserves the right to reject any and all proposals and will not reimburse offerors for any preparation costs.