Members are striking in protest at plans to close all Tube ticket offices and redeploy staff to ticket halls and platforms.
Unions say the changes, which will involve the loss of 750 jobs, will make the network less safe for passengers and have offered to suspend the strikes if the closures are put on hold.
LU denies suggestions that the closures will reduce safety and insist the redeployed staff will be able to better serve passengers than is currently the case.
They have also committed themselves to ensuring all Tube stations are staffed during opening hours.
Members will hold two 48-hour strikes, the first of which will start at 21:00 Tuesday, 4th February and last until 20:59 Thursday 6th February. A second strike will be held on 11 February.
LU plans to deploy back office staff to ticket gates and platforms in support union members who decline to strike. It will also use Travel Ambassadors to ensure Londoners are able to find alternative routes to work.
Transport for London says all non-Tube services will operate as normal, although some London Overground and DLR stations which interchange with London Underground may be affected by the strikes.
Passengers are being urged to plan ahead and to check before they travel at tfl.gov.uk and by following @TfLTravelAlerts, @TfLTrafficNews and @TfLBusAlerts on Twitter.
The following Tube services will operate:
