Insmed (INSM) had the highest return in January 2019 by a large-cap US stock, returning 86.6%.

ASSET	MONTH	% RETURN
Insmed (INSM)	January 2019	86.57%
Roku (ROKU)	January 2019	50.74%
Centrais Electricas Brasileiras (EBR)	January 2019	48.76%
EXACT Sciences (EXAS)	January 2019	45.57%
Companhia de Saneamento Basico do Estado de Sao Paulo SABESP ADR (SBS)	January 2019	43.81%
Centrais Elétricas Brasileiras SA - Eletrobrás (EBR.B)	January 2019	43.04%
Hess (HES)	January 2019	37.44%
GE Aerospace (GE)	January 2019	36.19%
Advanced Micro Devices (AMD)	January 2019	35.54%
Okta (OKTA)	January 2019	34.91%
Floor & Decor (FND)	January 2019	33.68%
Grupo Financiero Galicia SA ADR (GGAL)	January 2019	33.49%
PDD (PDD)	January 2019	32.77%
Pilgrims Pride (PPC)	January 2019	31.9%
Block (XYZ)	January 2019	31.89%
Flex (FLEX)	January 2019	31.42%
Aptiv (APTV)	January 2019	31.12%
Netflix (NFLX)	January 2019	30.94%
Texas Pacific Land Trust (TPL)	January 2019	30.65%
Tenet Healthcare (THC)	January 2019	30.35%
Teva Pharma Industries Ltd ADR (TEVA)	January 2019	30.25%
Tempur Sealy International (TPX)	January 2019	30.11%
Synchrony Financial (SYF)	January 2019	29.76%
Sarepta Therapeutics (SRPT)	January 2019	29.48%
Facebook (META)	January 2019	29.23%

Large-cap stocks are treated as having a market cap of $10B+.