Mixed milk feeding increases the likelihood of breastfeeding cessation, but it is not known if solid feeding (SF) has the same effect. We have identified 10,407 infants breastfed for at least 8-10 weeks from three large U.K. studies (Avon Longitudinal Study of Parents and Children [ALSPAC; born 1990-1991], Southampton Woman's Survey [SWS; 1998-2008], and Infant Feeding Survey 2010 [IFS 2010]) to investigate the associations between early SF and breastfeeding cessation. In the earliest study (ALSPAC), 67% had started SF before the age of 4 months, but in the latest (IFS), only 23% had started before 4 months. Solid food introduction before 4 months was associated with stopping breastfeeding before 6 months in all three cohorts, with little effect of adjustment for maternal sociodemographic characteristics (Poisson regression, adjusted prevalence ratios: ALSPAC 1.55, [95% confidence interval 1.4, 1.8], SWS 1.13 [1.0, 1.3], IFS 1.10 [1.1, 1.3]). Using Cox regression, adjusted hazard ratios for breastfeeding cessation compared with SF after 5 months were 2.07 (1.8, 2.4) for SF before 4 and 1.51 (1.3, 1.8) at 4-5 months for ALSPAC and 1.25 (1.1, 1.5) and 1.15 (1.0, 1.3) for SWS. Earlier introduction of solids was associated with a shorter duration of breastfeeding, particularly in cohorts where earlier introduction of solids was the norm, with a dose-response relationship, which was not explained by background social characteristics. As mothers most commonly introduced solids in the month prior to the then recommended age, continuing to recommend deferring solids to the age of 6 months is important to support sustained breastfeeding.