A highly efficient, broadband plasmonic absorber was developed for solar steam generation. This absorber, fabricated through self-assembly of metallic nanoparticles on a nanoporous template, achieves an average absorbance of ~99% across a wide wavelength range (400 nm to 10 μm). The structure consists of a nanoporous template with high porosity (≥40%) and randomly distributed gold nanoparticles, which enable efficient light absorption, strong field enhancement, and porous structures for effective solar absorption and heating. The absorber demonstrates over 90% efficiency in solar steam generation under 4-sun intensity (4 kW m⁻²). The self-assembly process allows for high-throughput manufacturing of nanophotonic structures and devices. The absorber outperforms previous plasmonic absorbers in terms of efficiency and bandwidth, and is comparable to carbon nanotube-based absorbers. The absorber is used for efficient solar steam generation, showing a 2.1 to 3.6 times higher evaporation rate than pure water under different solar irradiations. The plasmonic absorber's performance is attributed to its broadband absorption, plasmonic hot spot-enabled local heating, and multiple nanopore structures. The study highlights the potential of self-assembly in creating scalable, high-performance plasmonic absorbers for various applications, including solar desalination and sterilization.A highly efficient, broadband plasmonic absorber was developed for solar steam generation. This absorber, fabricated through self-assembly of metallic nanoparticles on a nanoporous template, achieves an average absorbance of ~99% across a wide wavelength range (400 nm to 10 μm). The structure consists of a nanoporous template with high porosity (≥40%) and randomly distributed gold nanoparticles, which enable efficient light absorption, strong field enhancement, and porous structures for effective solar absorption and heating. The absorber demonstrates over 90% efficiency in solar steam generation under 4-sun intensity (4 kW m⁻²). The self-assembly process allows for high-throughput manufacturing of nanophotonic structures and devices. The absorber outperforms previous plasmonic absorbers in terms of efficiency and bandwidth, and is comparable to carbon nanotube-based absorbers. The absorber is used for efficient solar steam generation, showing a 2.1 to 3.6 times higher evaporation rate than pure water under different solar irradiations. The plasmonic absorber's performance is attributed to its broadband absorption, plasmonic hot spot-enabled local heating, and multiple nanopore structures. The study highlights the potential of self-assembly in creating scalable, high-performance plasmonic absorbers for various applications, including solar desalination and sterilization.