In case you have <TextField... in Material UI and have a border

border outline in TextField in MUI

<TextField
                            placeholder=""
                            
                            fullWidth
                            multiline
                            rows={7.5}
                            maxRows={Infinity}
                        />
                        
                        
                        // Just put this CSS
'.MuiOutlinedInput-notchedOutline': {
                                border: 'none'
                            }