The accomplishment of 1D semiconductor nanowires (SN) in the field of energy has attracted intense interest in recent years due to their advantageous properties (e.g., large surface area, unique surface chemistry, and tunable transport properties). Considerable efforts were devoted to explore 1D-SN building blocks as the harvesting channel/unit (e.g., in thermal, chemical, mechanical, and solar energy applications) and as the storage media (for electrochemical energy). A wide bandgap tuning of SN in the range of 0.39 eV (in case of InAs nanowires) to 4.66 eV (in case of β-Ga2O3 nanowires) due to quantum size effect makes them a suitable candidate for optoelectronic applications. This review focuses on 1D-SN wherein the travel of electron and photon is confined in two directions but in one dimension. The SN emerged as promising nanostructures for developing electronic devices of high carrier-mobilities (e.g., >12000 cm2V−1s−1 for holes and 3000 cm2V−1s−1 for electrons in case of Ge nanowires). A list of efficient fabrication strategies (e.g., vapor-liquid-solid [VLS], hard-template approaches, and solution-phase) are discussed along with ultrafast electron transport dynamics of SN and piezoelectric nanowires. The control on electrons, photons, and phonons transport makes 1D-SN ideal for solid-state energy conversion, harvesting, and storage applications. State-of-the-art 1D-SN energy nano-systems have been demonstrated to yield diverse outcomes of high significance including single-nanowire and array-based photovoltaic cells (InP nanowires with a maximum power conversion efficiency up to 17.8%), nanogenerators (SiGe nanowires with a maximum power output of 7.1 μW/cm2), supercapacitors (core-shell hierarchical CoS@MoS2 nanowire array with an energy density of 95.7 Wh kg−1 at power density of 711.2 W kg−1), and lithium-air batteries (3D freestanding hierarchical CuCo2O4 nanowires@Ni foam with an excellent specific capacity of 13654 mAh g−1 at 0.1 mA cm−2). This review will serve as a key platform to understand 1D-SN to fabricate the next-generation novel nano-systems for developing efficient energy devices of high performance.