A comprehensive transposon mutant library of *Pseudomonas aeruginosa* was developed, containing 30,100 sequence-defined mutants with an average of five insertions per gene. This library provides nearly complete coverage of the 6.3-Mbp genome, with about 12% of predicted genes lacking insertions, many of which are likely essential for growth on rich media. Statistical and bioinformatic analyses suggest that approximately 300–400 genes are essential for *P. aeruginosa*. The library was generated using transposon mutagenesis with ISphoA/hah and ISlacZ/hah, which allow for the detection of gene expression, protein localization, and epistasis. The mutant collection was used to screen for defects in twitching motility and prototrophic growth, identifying nearly all genes expected from previous studies. The transposon insertions were mapped using PCR and sequencing, and quality control confirmed the accuracy of the insertions. The library provides a valuable resource for studying gene function and has potential applications in drug development and understanding the complex biology of *P. aeruginosa*, which is a major cause of infections in cystic fibrosis patients. The library also allows for reverse-genetic studies and the generation of double mutants for epistasis analysis. The results highlight the importance of comprehensive mutant libraries in understanding the genetic basis of bacterial traits.A comprehensive transposon mutant library of *Pseudomonas aeruginosa* was developed, containing 30,100 sequence-defined mutants with an average of five insertions per gene. This library provides nearly complete coverage of the 6.3-Mbp genome, with about 12% of predicted genes lacking insertions, many of which are likely essential for growth on rich media. Statistical and bioinformatic analyses suggest that approximately 300–400 genes are essential for *P. aeruginosa*. The library was generated using transposon mutagenesis with ISphoA/hah and ISlacZ/hah, which allow for the detection of gene expression, protein localization, and epistasis. The mutant collection was used to screen for defects in twitching motility and prototrophic growth, identifying nearly all genes expected from previous studies. The transposon insertions were mapped using PCR and sequencing, and quality control confirmed the accuracy of the insertions. The library provides a valuable resource for studying gene function and has potential applications in drug development and understanding the complex biology of *P. aeruginosa*, which is a major cause of infections in cystic fibrosis patients. The library also allows for reverse-genetic studies and the generation of double mutants for epistasis analysis. The results highlight the importance of comprehensive mutant libraries in understanding the genetic basis of bacterial traits.