Loomis Sayles Income FundLoomis Sayles Income FundLoomis Sayles Investment Grade Fixed Income FundLoomis Sayles Investment Grade Fixed Income FundDretailandinstitutionalprospectus_4830Loomis Sayles Funds I - Classes Admin, Retail, Institutional, and NDretailandinstitutionalsai_48215-1 Retail and Institutional SAIClass Institutional - C000018122InstitutionalClass Retail - C000018123RetailClass Admin - C000018124AdminClass N - C000125493NClass Institutional - C000018133InstitutionalDistribution Rate RiskDistribution Rate RiskPortfolio Turnover Rate RiskPortfolio Turnover Rate RiskBloomberg U.S. Aggregate Bond IndexBloomberg U.S. Aggregate Bond IndexBank Loans RiskBank Loans RiskCredit/Counterparty RiskCredit/Counterparty RiskBelow Investment-Grade Fixed-Income Securities RiskBelow Investment-Grade Fixed-Income Securities RiskInterest Rate RiskInterest Rate RiskCurrency RiskCurrency RiskMarket/Issuer RiskMarket/Issuer RiskCybersecurity and Technology RiskCybersecurity and Technology RiskDerivatives RiskDerivatives RiskEmerging Markets RiskEmerging Markets RiskEquity Securities RiskEquity Securities RiskForeign Securities RiskForeign Securities RiskLarge Shareholder Transaction RiskLarge Shareholder Transaction RiskInflation/Deflation RiskInflation/Deflation RiskLeverage RiskLeverage RiskLiquidity RiskLiquidity RiskManagement RiskManagement RiskMortgage-Related and Asset-Backed Securities RiskMortgage-Related and Asset-Backed Securities RiskREITs RiskREITs Risk